ok they were hitting with flat tops right?
if so look for a dish piston not a dome
or find one with a smaller compression height
im not sure on a bbc but a sbc stock is 1.560 and a lot of oem replacements are 1.540
meaning the piston will not rise as high in the cylinder
try looking at silvolite there an oem replacement made by keith black not sure if they will have for your application but worth a shot
hope this helped
-logan