Don’t know the exact configuration but you start with a 413 big block usually found in old Dodge gas tandems, I think a 440 crank. And a set of stage 4 heads and you have a 426 max wedge. Which is an option for 63
The guy has a 426 Max Wedge with cross ram intake to fit under the hood. It will be one sweet ride. Just hope I have enough left in me to do a good job on the body work.