OK, not to beat this into the ground, but, yes, off the shelf pistons are available for 413's, but - they are low compression cast pistons. If you want a modern, lightweight, forged, zero-deck, off-the-shelf piston for your 413, you're out of luck.
And actually, I do have a 413. It was in the car when I bought it. Its pistons are .080 below deck at TDC, but Edelbrock heads milled .050 brought the CR up a point or so from the maybe 8.5 to one it had before. Runs well enough for a strictly street motor, and keeping it is a lot cheaper than building a new motor. If I were building a big block from the ground up, I'd start with something else.
View attachment 1715737799
