How do I Figure out what Rod Length to use?

Hey everybody, I am new to Alcohol racing. I am used to working on Fuel cars. I am trying to build an Alcohol Dragster. Since my dragster will be a bit on the heavy side, I believe I want to either run a 471 or 481 Hemi. The 471 with a 4.250" Bore and a 4.150" Crank. The 481 with a 4.375 Bore and a 4.000" Crank. I am not sure which is the better combination if either of them is at all. The question I have is what length rod do I use with these combinations? and how would I go about figuring this out?

Thanks everyone for any information you could provide!