Thanks. You're right, the Chevy spec sheets do say that it uses a 4.74 inch bolt circle. I wasn't sure about the Rocket 88. I was hoping that there might have been some consistency along the GM lines, but I guess that wasn't the case back in the 50s and 60s.
On a technical note, can you tell me if this is the method used to measure the bolt circle diameters as we've been referring to the measurements? I'm not confident in my own measurements, so I thought it would be a good idea to double check.