advice on new wheels, tires and brakes.

So after mostly full season of auto cross, the shortcomings of project frankenfiat are very clear.

In order of how bad they are

1. Driver (my gosh I can't put togehter clean runs consistently)

2. Brakes

3. Tires

Unfortunately numbers 2 and 3 are greatly hindered by my current 13" wheels.

So I'm going to turn to the GRM brain trust to help me figure out what wheels and tires and brakes I need.

Information

68 fiat 850 spider body abarth A arms and coil overs in front.
Rear end is a VW IRS set up

Total weight (with driver) 1684 lbs Front 548 rear 1136

First two autocrosses were disasters. The front brakes are wilwood discs, 9 inch rotors with this caliper wilwood front

while the rear were stock VW drums. As was expected, this lead to locking up the front and sliding like I was on glass.

I put in a brake proportioning valve, and if dialed all the way down to reduce pressure to the front, braking was better, but still not anywhere near good enough to be competitive.

This winter I want to get 15" rims to clear better brakes, and fit good tires. Currently I'm running 205/60 r13 federal 595's. While they were good, Right now the tire I'm leaning towards is the new Rivals, but could be talked into just about anything.

There are a myriad of rear brake kits that will bolt on to the rear VW setup. I'm trying to figure out how much brake I need. The kits run anywhere from $275-$1500. the high end ones are for heavy sand rails with hardly any brakes in the front, so I know they are more than able to handle my light little car. I want to have plenty of brakes in the rear to handle it with the new stickier tires, but don't want to spend more than I have to.

also, for the wheels and tires, should I run staggered sizes?

If your weight distribution really is ~30f/70r i would think a staggered tire setup might not be a bad idea.

Hell, at that point ADDING weight to the front end might make it stop better.

Are your front dampers double adjustable?

Hard to say which rear brakes you should buy because i have no idea what the options at the low end of the spectrum are. Can you put bigger wheel cylinders in the drums you have now? Chamfer your front pads to reduce effective pad area and fudge the bias away from the front? Turn compression all the way down on the front dampers so you transfer a little weight forward under braking?