I am getting ready to rebuild my 420a and i cant find a block at a junk yard to tear it down and rebuild. So i'm probably just going to rebuild the one that i have in my car now. I figure it will probably take 3-4 days to pull it out and rebuild if everything goes smoothly. Motor is in good condition, 104,000 miles, runs great but a leaky head gasket so i'll put a new one there. What do you guys think are the chances that i'll have to go bigger than standard main bearings? It's not too high of mileage i dont think, and i dont beat on it too hard. What do you guys think? Thanks

Its true its only 104k Mi, and YOU don't beat on it... but who owned it before you? did they? I vote get the machine shop to check it, or plasti-gauge it to see if it is within specs if it isn't all scratched. if nothing else get it polished up nice. From what i've read though, bearing should be fine unless you spun one? thats my .02$

yeah you shouldn't have to go oversize unless you spun something and/or the crank is scarred to where the machine shop would have to turn it. It's always a safe bet to have the shop at least check it, though.

If your bearings aren't spun, you should be able to pick up a set of new stockers and just install them. Just be sure to pick up the $5 pack of plastigauge and check your tolerances before you button it all back up.

You can probably also get away with a nice hone job and some fresh rings. If you're not pulling the block out to have a shop bore it for larger pistons, I'd suggest new, stock rings, a hone and re-using the your pistons and rods.

Three to four days is going to be a rush, though. Good luck with that.