Help identify L28et pistons

[ezzzzzzz]

I picked up an 82 280zxt (with 201300 miles on the OD) the other week. The F54/P90a engine supposedly had no compression on cylinder 5. Someone had pulled the valve cover, water pump, oil pump, etc. for reasons I'm not sure about. I pulled the engine yesterday and removed the head expecting to find a burnt valve, blown head gasket or damaged piston/rings. Nada...nothing wrong. There's lots of oil every where and the plugs were heavily fouled. The block has no ring ridge and crosschecking is still evident in the bores. One of the torque convertor bolts was lightly damaged. I'm convinced this is a relatively recent rebuild. All of that said, I am wondering if this is an overbore or ridge-reamed block. The pistons all have P90 stamped into them. Four of them are also stamped 23 (1,3,4,6) and two are marked 45 (2,5). Can someone possibly help identify what I have here?

[Bubbleguinea]

? if it was an overbore, it would have a decimal number imprinted on the piston surface...like mine says ".5" for .020 overbore...did you get a history of the rebuild? like from the guy/girly you bought it from?

[ezzzzzzz]

No information is available. I picked up to car as an abandoned vehicle. It was driven in but left behind after it appeared to be a money pit. The property owner just wanted it gone so we came to an equitable agreement and I towed it away. I haven't cleaned to piston top(s) fully so I don't know if there is any overbore info. The cylinders do not appear to have been ridge reamed. It was the different numbers on the pistons that had me curious. I could use a bore gauge to determine any taper and/or overbore of each cylinder.