I have an '80, and there are a few other members with Miradas as well.

Mine "feels" pretty light to me, but I've never weighed it. People on the race forum say they are 3600lb+, but I'm not sure I believe that. Underneath the skin they are basically the same car as a 1976-89 Aspen/Volare/Diplomat/5th Ave.

Only 1980's came with the 360, 81-83 will either have a slant 6 or 318. The usual hot rod parts apply like they do to any other engine. A 4 barrel intake and carb (if it's a 2bbl) and headers are a good start. Hedman headers part #78050 meant for an A body fit perfectly, that's what I have on mine.

Mine was originally a slant 6, I built a mild 360 for it and swapped the weak 7 1/4 rear for a 8 3/4.