The guy says they are 3 15/16". I think that is max overbore according to California Bill Fisher. Not a bad price if you compare to custom built.

https://www.ebay.com/itm/325420976274

Those are fifties and earlier technology--hasn't someone come up with a MODERN piston & rod combination? Seems Buick rods are longer and can be used, I've used ring spacers with much thinner rings in old pistons that originally used very thick rings which beat the ring lands up--what's the current skinny??

Yeah well. These "fifties and earlier" engines are not as easy to find parts for as they were when I built my 270. 270 pistons in any form are getting harder to find. I have a set of these or I would not have posted this link.

All 228-302 GMC rods are basically the same (7"). There is a small end bushing thing and a bottom end insert notch difference. All can be made to work and are strong rods, plenty for most of us. For those looking for old parts upgrades there are (8") Hudson rods used with MOPAR inserts that can be used with lighter custom pistons.

I just thought after previous post here looking for 270 pistons someone might be interested.

GMC L6 rods: 7.00" long, 2.311" journal, .990" & 1.0524" pin
Buick 320 L8: 8.25", 2.250", .875"
Hudson 308 L6: 8.125", 2.125", .968"; this does not inspire confidence

Sorry I posted about the Pistons that work with stock GMC rods.

I just looked and cant see that they have pins.

I agree, no pins are shown, and the usual rule is "only what you see". The perspective of the photos makes estimating the pin diameter (which I can sometimes do in Photoshop) impractical.

Those instructions are a bit scary. Mill the block (is that .125"? it's hard to see) to get the CR up suggests that there is no quench with stock deck height.
Perhaps with that mill the dome is flush with the deck, and the gasket thickness is the quench clearance?
Alcohol?
The description also says "270 head", but from the dome shape it only fits one type of chamber.

It's a good price if you can use them "as is", but if mods are needed a custom piston becomes more practical.