As already written, standard pistons were 73mm with three factory oversizes in half mm increments [73.5, 74 & 74.5 mm]

If you use A12A or late model A13 rods you can bore the block to 75mm which is A12A size along with three oversizes in half mm oversizes.

Additionally you could bore it to 76mm & use A13 or A14 pistons. Both of these come in the same three oversizes but pushing it beyond 77mm is probably pushing your luck a bit.

Why the different rods? The 73mm pistons [& oversizes] used a 17.5mm wrist pin while all other models used a 19mm pin.

The A12A & late A13 were simply bigger bore A12 blocks but their rods had the larger eye to accommodate the larger pin.

Later A12 rods were forged with the larger 'little end' but were bored for the smaller pin, These can be bored out with confidence.

I wouldn't actually recommend boring the earlier rods with the smaller 'little end, yet this is what I did in my GX engine in the early 80's & drove it for squillions of miles without any problems.