Need some help with a trans bolt up problem

My buddy has a '66 with a c4, his bro. gave him another c4 to get rebuilt for the '66 so he wouldn't have to pull his till later. He took the torque converter from his original in to the shop so they could make sure they got him the right one and it doesn't fit the replacement trans do to the replacement being for a '70 and on vehicle and the bell housings have diferent bolt paterns so he cant just get a new converter and switch bells, is there an adapter to be able to use the '70's trans on the earlier models, or is he going to have to just get the other rebuilt?

D.Hearne said:

All 289 blocks from 65-on have a 6 bolt bell housing pattern and are completely interchangeable with the 302's. The early 65 blocks (64-1/2 cars) had the earlier 5 bolt bell pattern. In the 70 model year, the input spline was changed from the earlier pre 70 24 spline to a 26 spline. So in effect the torque converters aren't interchangeable between the 70-up and 69-older C-4's.

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Are you able to just switch the old trans model for the new model completely? Will there be any linkage or other problems, will the flywheel/flexplate for the earlier model engine bolt up to the newer model torque converter, is the output spline diferent, did they change the mounting pattern on the bell housing where it connects to the block?

Never mind just found out he took his other trans down and paid for the one he got rebuilt now he has a 70's c4 thats rebuilt and no use for....oh well his money, I would have figured a way to make it fit if possible. Thanks for the help anyhow.