i took my 455 apart the other day and made an odd discovery. The cylinder bores are nice with cross hatch pattern, the pistons are stock and have "buick" stamped underneath, the engine appears to have been freshened up with new bearings at one time. first off the cam bearings are trash but the mains and rods look good. I knocked the pistons out and low and behold on the front of the crank was written: rods 10 - main 30. so would you run it at 0.0030 at the mains bearings, and 0.0010 at the rods if i popped for a bore, pistons, and fresh bearings?
30 under is pushing it. If its got any grooves, it may be too undersize afterwards. A stock crank is cheap. Get a replacement standard crank and bring it to a machine shop. Have them measure it. In a best case, it will just need to be polished.
.030 is not a problem from a strength standpoint. They take .200 off of small-block Chevy 400 cranks to put 'em in SBC 350 blocks. Pontiac guys used to knock .250 off of 455 cranks to install in 400 blocks. The only issue is whether the crank can be used at .030; or whether you can get .040--.060 bearings if it does need to be cleaned-up.
If all the journals check out throw it back in. Good Luck. If you don't want to do that I have a standard crank. $100.00 plus shipping Bob H.
