hello so it kind of depends what your going for auto or standard and how much work to the engine you plan on doing? just some rough knowledge i have is pre 1985 musang 5.0 has a flat tappet cam and is factory carb not that great out of the box after 1985 roller cam factory holley 4 barrel carb or tbi on some starting on the 1984 gt350 edition car, 1986 factory fuel rails and a modern intake but speed density harder to modify unless mass airflow converted so post 89 has the be the better starting point mass airflow roller cam if you keep efi. then the transmission is the next question t5 is awesome out of the box stock on the stang other the the syncro issues they get. auto transmission you have 3 option that came in the stang AOD (not that great IMO if you messup line pressure they blow up) c4 basically bullet proof but no over drive gear so worse fuel economy on hiway. then my personal favorite the 4r70w its computer controlled has over drive and converter lockup great on highway and fairly reliable and cheapish. ive bought them from $150-$500 i put one behind the 5.0 expo swap i did to make it 2wd (was an awd truck), plugs write in pre 2004 trannys that is (out put shaft speed senor changed along with the drum inside the tranny it reads lean from my mistake). Also put one behind my 88 ranger v8 swap with a carb. v6 4r70 is the cheapest and it has the small block bellhousing pattern 3.6 v6 and 4.2 v6 use it that's what mine are. sorry for the long wright up if you have questions ask away i"ll try my best to help and I hope this helped a bit