65 Fastback help

I have got a 65 fastback that is pretty much completely set up it ran good but when i went to get it dynoed the tranny went out on the first run. I talked to the guy that runs the shop and he said that he can fix the whole thing for me it just depends on how far i wanna go. So i got to thinkin I am tired of the 289 and C-4 problems that I keep runnin into so i am thinking that i should go with a C-6 and 351 bored out to a 427. which in my thought means both being carte engine and trans that i shouldnt have a problem for some time. Anybody know roughly how much i am looking at spending or have any suggestions for me

Well if you wanted to bore a 351 you would have to stroke it too to get it to a 427. Decide what you want to do either BB or SB and then go from there.

im gonna go with a small block cause of weight and boring and stroking the engine was part of the plan i just put them together when i think about it, my fault for confusion