Help with trannys? 🤔

[HoneyBeeMan68]

So I was reading cjoenny89 new clutch not disengage and it made me think about what I have. So I have a 68 long stepside which should have a 327 3 on the tree in it . But the 1& 2 owners blue up the motors that they put in. The 2 motor was a 305 with the tranny all cast iron gm 163952645 a190 e10 tail 3860042 gm 32 main body gm26 3926647 e600 ( I think Saginaw 343) and was given a free tranny marked cast iron gm122952647 d23 f64 main body gm338835 #2 tail 6261884 gm4 . I think from pictures it’s a Saginaw 456 . Sorry for the long info, but I have a blueprint 355 and some friends say the 3 speed will not handle the motor so before I buy my pressure plate I was hoping to get more insight for you guys! The picutes show different tail housing on them. My question is a: can I use what I have or will I need to go with a 4 on the floor?