to put a 700R-4 From a 4.2L Astro Van 91- up into my 700R-4 equiped 1987 Firebird Trans Am 305 TPI do i have to change the bell housing? the spedo sending unit? see my trans am acts like it lost 3rd and 4th gear it just revs up like nuteral when shifting into third so im looking for a cheap replacment

 

you'd need to figure out a way to mount the torque arm. is it a 4.3 and not a 4.2? if it's a 4.3 the bolt pattern is the same so all you'd need is the torque arm. easiest way to do that is trash the stock piece and get an aftermarket one that doesn't attach to the trans. not sure but i ihink the 91 trans has a mechanical speedo.