the best thing to do it is look into your cylinder and check to see if there's any deep scratches...depending on the depth of the scratches, you need to determine the size of the piston you will need. the metra 65ccs come in 43.5mm(stock size), 43.7, 43.9, 44.1, and 44.3mm oversize pistons....when overboring you want to make sure that your not left with any scratches... as it defeats the purpose, as it may cause blowby
greg sorry but that's not the way to do it, as stated above the pistons only come in certain sizes...purchase the piston first, bring the piston and cylinder to the machine shop...they're gonna measure the piston size with a caliped....then they're gonna bore the cylinder to the size of the piston with a certain tolerance for piston expansion etc....you might wanna ask benji or 1977 if they have oversize pistons.... or order from metrakit themselves