Help me build a Cadillac in my head.

So I used to have a 1984 Cadillac Eldorado. Looked like this: 

So it had the junky HT4100 in it, but my uncle took good care of it and I had around 250k on it when my mom sold it out from under me. I’ve always kind of wanted another one. 

My thought is, would an LS motor bolt up to the transmission? 

The ‘79-‘81 cars had the TH325 3-Speed Auto and the ‘82-‘85 cars had the TH325-4L 4-Speed Auto. Both these transmissions shared internal parts with the TH200 and TH200-4R. 

On the Olds Toronado of the same years, they used either an Olds 350 or Olds 307. As far as I’m aware, an LS truck motor should bolt up to whatever they bolt up to. I thought a stock 4.8L would be perfect for this car. 

Is this at all possible? I would love to have one of these as a highway cruiser again, but with a more modern, reliable motor. 

I’m also curious if you can make the Digital dashboard continue to work as well. 

I’m not sure if there’s any other mods you can do to an E-Body. 

In reply to SyntheticBlinkerFluid :

If it used a normal Olds motor it's the wrong bell housings pattern. BOP pattern is different from SBC. While as far as I know the LS pattern is SBC plus a top center bolt. 

I would probably look at how hard the mount and axle situation would be on a 3800SC/4t65e or LS4/4t65e combo from a w-body. 

I googled and the E-body platform was also used for the Rivera in those years. And that car was offered with Buick V6s. Also available in turbo flavor. And this is where I remember why almost every front drive Cadillac is more interesting to me in Buick flavor becsuse it seems most Cadillac specific engines were garbage.

I have thought I’d like a bustleback Seville with either real Caddy (500 ci) power or the Trailblazer SS drivetrain and AWD.

If it’s just a bop trans a $60 adapter fixes that

Patrick said:

If it’s just a bop trans a $60 adapter fixes that

Ok the man's got a point.

Ht4100 is GM metric pattern so LS4 it?  LS4s are cheaper and already set up for fwd.

This old thread will lead you to the Cadillac that I'm building in my head. 

Stampie said:

Ht4100 is GM metric pattern so LS4 it?  LS4s are cheaper and already set up for fwd.

That’s a good question. I knew the HT4100 was a metric pattern, but I didn’t know the LS4 was too. The only thing to take into consideration is the oil pan. The engines in these old E-Body cars are longitudinal FWD, those LS4s were transverse. 

In reply to Daylan C :

I’d rather keep it’s in its Longitudinal FWD setup. Since the TH325 uses 200-4R parts, it can be upgraded to handle more HP, which anything over the 130hp is more HP. 

Standard not backwards intake from any LS should work, if the water pump and front accessories swap over too that would just leave you with the oil pan and pickup to deal with. 

I suggested the w-body engine and trans because I didn't know the e-body was longintudinal.

Stampie said:

Ht4100 is GM metric pattern so LS4 it?  LS4s are cheaper and already set up for fwd.

What's the starter situation on the trans? That's what kills LS4 manual trans swaps.

In reply to Will :

IIRC, it’s in the same place most GM Small Block starters are, lower right side of the motor. 

If I remember correctly from my own bench build of a similar project, the deep skirt of the ls block interferes with the output shaft of the differential.  The shaft passes through oil pan of the BOP motors, but hits the deep skirt on ls motors.  I found diagrams of the conflict on a kit cars site years ago, I do not remember which one.

You could certainly get a Cadillac 500 in there. The 368 that these cars had originally is the same basic block just with less bore.