You need to say what
trans/engine is in the car now and if you like it-auto or manual. if your car has a 4 speed(manual) in it I would stick with it unless you like autos. It might have a 3 speed manual though-not as good. If it has an auto in it and it has a 390 in it already it'll be a c6 auto
trans-bulletproof. If it's a 289 or six it'll have a c4 damn good
trans too. changing form a manual to auto requires a lot of parts that will be relatively hard to procure(and expensive) given the vintage year and for a 390 in front of it.