Circle Track stuff is commonly 5/8-11 studs - you hammer out the stock studs, drill & ream the holes to 43/64" and then hammer in new splined studs. Therefore going back to a stock 7/16" stud isn't going to happen. The one thing to check - you could pull your drums and by chance maybe they drilled a new pattern instead of enlarging the stock ones - then you could insert new studs into the old holes.
Another note - if that 7.5" has seen any time in a circle track car you may really want to consider buying a new set of Moser axles - they are about $235 a pair and are much stronger (along with having the correct size holes for stock studs). It is very common to fatigue or flat out break a stock 7.5" axle and I've bought at least one dirt car in the past that has had a bent axle upon inspection.
Hope this helps you out some - one class I run limits me to a 7.5" rearend so I've got a little experience in breaking them and then making them durable (in that order!). Jim
Another note - if that 7.5" has seen any time in a circle track car you may really want to consider buying a new set of Moser axles - they are about $235 a pair and are much stronger (along with having the correct size holes for stock studs). It is very common to fatigue or flat out break a stock 7.5" axle and I've bought at least one dirt car in the past that has had a bent axle upon inspection.
Hope this helps you out some - one class I run limits me to a 7.5" rearend so I've got a little experience in breaking them and then making them durable (in that order!). Jim