eatinJDM

Hey all, I've been wanting a ls powered third gen for about 5 years, finally starting on my build with a 84 z28 roller and fbody ls1/4l60 I've recently purchased. Ill start a build thread on that in a bit. One thing I've always wondered is why ls1 third gens always seem to run a few tenths slower than ls1 4th gens? The third gens are lighter and have the same suspension minus it being 20+ years old. I had a 98 z28 with a circle d stall and some bolt ons and loved the power but was never happy with 4th gen looks. Loved third gens since my first one at 16. Is there any major areas on a third gen that need updating/modifying to get the 4th gen feel and lose all the rattling and squeaking in my 84 z? Obviously ill refresh the suspension but is new shocks and poly bushings on the whole car going to suffice or should I save up and order the entire umi, bmr, spohn catalog. My budget left for the build is around 4000, I already have the car, engine, trans, ecu, ls1 driveshaft, m6 ls1 rear and painless harness. Thanks for all the help in advance