Small bolt pattern VS. Big bolt pattern

The bolt pattern size has no bearing on the strength of the axles. The bolt circle size didn't have any bearing on drum size other than only A-body cars used the small 4" bolt circle and they only came with either 9" or 10" drums and the rare Kelsey Hayes disks up front..

However, the small 4" bolt circle used 7/16" studs to hold the wheels on and the 4.5" bolt circle used 1/2" studs so there is a strength advantage there. Also, there is a strength advantage to the large bolt circle in regards to side loading of the wheel. With the bolts further from the center line there is less moment arm for side loads to try and pull the lugs through the center of the rim.

The only real significant advantage to the large 4.5" bolt circle is the availability of wheels. Stock small bolt circle wheels were limited to 14" by 5.5" wide and there is little or no availability in after market wheels though places like Wheel Vintiques make the ralley style wheel in 15" and up to 8" wide. In the 4.5" bolt circle the sky is the limit in regards to wheel choices.

Unless your plans are for a 500 HP car don't limit your self to an 8.75 axle. 73-76 perfromance A-bodies came with an 8.25" axle that has the larger 4.5" bolt circle and is more than adequate for a perfromance small block a-body that is going to be a street car.