(1) 068 clone, such as a Melling SPC-7
(2) Summit 2801, which is a high lift version of an 068
(3) Lunati 10510312
(4) 744 clone, such as a Melling SPC-3
(5) Summit 2802, which is a high lift version of a 744
The next size up is probably a Crower 60243. But, they cost a lot more, and I think are probably a little more cam than a mild street 400 needs.
"...get the motor back to the 10.75:1 compression..."
If you build with that much compression, you'll need to add a good octane booster, like Torco Accelerator, or mix in some race gas, or switch to E-85. Otherwise you could have detonation problems. Most Pontiac engine builders today, recommend no more than 9.5:1 CR, with closer to 9:1 being safer, with today's pump gas.
If you are rebuilding the short block, you can go with dish pistons, to reduce your CR, using the 72cc heads. The cheapest would probably to buy the Speed Pro forged L2262F pistons & have a competent machine shop cut a dish in the top. This is a common practice.
Icon makes a 400 piston with a 14cc dish. They are about $500 + shipping.
If you're gonna buy forged rods, you might be able to use some SP WL2323F 455 Olds pistons, with some H-beam rods. These pistons are around $320 shipped. They have an 18cc dish and a slightly higher pin height, which should put the piston top near zero deck, without cutting the decks down any. The SP cast 455 Olds pistons are cheaper & should be plenty good for a decent street 400 build.
We've been discussing this on the PY site. Not positive it'll work. But looks like it might. I offered to buy one of the pistons, so an engine builder could try one & see if it will work. So far, no takers. I'll make you the same offer. If it won't work, you can just throw the piston away. If it does work, all you have to do is buy 7 more pistons.
The RPM Pontiac H-beams are $400 shipped.