Best Performance Upgrades for Little Money - Here's My Vote

I loved roaming the junkyards for parts, the cheapest upgrade was putting a 383 in the fastback, hoisted it in and dad fabricated the motormounts from a templet he found in an old hotrod mag. we found every part we needed in the yard, manifolds, headpipes, tranny, 8 3/4 axle, ......... ya get my drift. for the wopping cost of 100 bucks.
the year was 1978. lol those were the days. we built a lot of low budget stuff from other peoples junk.