I'll offer a quick synopsis of the diesels I like. It's not a definitive list, but it might give you something to shop for and see if you can find some gems in your budget. The "diesel tax" you refer to is real, but it completely works in your favor. Yes, higher buy-in, but way better sell value. None of my diesel trucks ever lost me any money with one exception. I paid $10k for a diesel van, drove it for 40k miles and resold it for $9k. The rest I waited for a bargain and either broke even when I sold, or made money. My best one was breaking even on a 95 F250 powerstroke that I drove for 6 years and put 75k miles on it.
First, a general thought. Most of the diesels I list below I have chosen for their durability and low maintenance costs. Any of them will probably run for 300k miles without ever needing anything but maintenance. Having said that, the rest of the truck that surrounds the engine is another story. It is no different from any other vehicle, and after 300k you might have a rusted frame, electrical issues, suspension issues, etc.
One other general thought. If you haven't owned a larger-displacement diesel like these trucks have, don't get caught up with HP and TQ numbers. The 6.5L chevy I had was rated at 180hp and around 400 lb-ft of torque. That doesn't sound special, but diesels tend to make much broader torque curves. In a gas truck with the same numbers, they only make those numbers immediately surrounding the RPMs of their peaks. With diesel, they tend to make that same amount of output over a much broader range of RPMs. Like I had mentioned before. My 6.5L could tow 10k on any grade it encountered and never fall below the speed limit.
6.5L TD (chevy/GMC, late 1992-1999). Indirect injection means a bit higher compression than many diesels, but that really helps at the pump. Great MPGs in the low-mid 20s. Detroit design, crazy bulletproof. It is advised to relocate the computer from the side of the engine to the inner fender to prevent heat from eventually cooking it. Most of them are going to be really beat at this point, but if you find a low-mileage example, chances are it won't command a huge price with the number of more modern diesels making monster power numbers. People dismiss them, but they are great diesels IMO. The truck and transmission that surround the engine are reliable as well.
7.3L Powerstroke (94.5 - 03 Ford). Very similar to the 6.5 TD, but direct injection. Modest power outputs in the 215-265 hp range, but mountains of torque. Trucks tend to rust relatively quickly, but the transmissions are fairly bulletproof at stock power levels. The TC likes to develop a shudder during lockup which can be nursed along for about 30k miles with an additive called "shudder fix." Starting with the 99 trucks (the newer body style) they got an intercooler which is only really a benefit if you are planning modifications. The downside to the newer trucks is the sloped windshield and firewall making maintenance and repairs a bit less comfy.
6.0L Powerstroke (04-07 Ford). The 6.0L has issues - namely EGR cooler and oil cooler. They are expensive and difficult to fix (called bulletproofing), but once fixed they are a great diesel. Find one that is bulletproofed (and can provide receipts) and it is a good bet since its reputation keeps values a little lower.
LB7 Duramax (late 99-04 chevy/gmc). Wonderful engines that had injector issues. There was an extended warranty added to those trucks, but it has long since expired. The fix was new/improved injectors that were an expensive and difficult repair. If you find one that has already been repaired (or one that needs injectors and negotiate accordingly), they are fantasmic. I have an 04 with 30-over injectors, a lift pump, intake, exhaust, 5-position chip, and a couple other mods that puts 938 ft-lbs to the wheels on a stock Allison transmission. It has 148k miles of hard towing abuse and it just won't quit.
LLY/LBZ Duramax (05-07). These two engine codes are very similar, but they got funky with which code went with a certain transmission or vehicle. Somewhere in these years the trucks went to a 6-speed version of the Allison trans. The 6-speed is pretty much the same trans, but what I find is that the programming of the 6 speed makes it a much nicer unit over the earlier 5-speed.
LMM Duramax (Late 07-2010). Also a fantastic diesel, but they came with a DPF that royally kills MPG. It is also highly unlikely you'll find one in your budget.
12v Cummins (89-98.5 Dodge). Early versions (up through 93 I think) used a VE pump and were pretty low output. They would run forever... VERY SLOWLY. The second version of the 12v used a P7100 pump that was not super powerful, but ridiculously easy to modify with a screwdriver for bigger power. It was all mechanical, and this was the engine that really put reliable diesels on the map. The biggest downside to the truck was the transmissions Dodge used. The other manufacturers (with a few exceptions) did clean-slate designs and built new transmissions. Dodge kept re-hashing versions of the A518... which was an OD version of the 727... which has been around since the early 60s. A518 - 46RE, 47RE, 48RE.... are all basically band-aid patched 1960s-based transmissions that were just too small for the torque and vibes from the Cummins. The 48E finally got things under control... as long as you resisted the urge to modify power.
24v Cummins (99-02 Dodge). Late 1998, they went to a 24-valve design with electronic controls. Still fantastic and darn near bulletproof, but the VP injector pump was a common failure point. If they starved for fuel for even a very short period of time, the lack of lubrication killed them. The solution for better reliability is a good air-separating fuel lift pump.
My dream truck is an F250 shell (ergonomics, assembly quality, ride quality) with an Allison transmission (very strong and fantastic) with a Cummins 12v/P7100 (bulletproof, easy to modify, all mechanical for simplicity). I've actually seen this combination done before, but how much money did they spend putting a Dodge engine and a Chevy transmission in a Ford truck?
