I just picked up a 454/4 bolt main, fully dressed motor. I plan on reusing as much as I can (accessories, rods, crank).
I want to up the compression with a set of flat tops so should I bore it or just leave it alone? What should it be bored to?

My plans are a street/strip build with machined 781 heads.

Common overbore is .030 and .060".

Everything you know about SBC doesn't always work with a BBC. Larger combustion chamber sizes allow for larger unshrouded valves. Domed piston can be easily used to increase the compression ratio to what you want. If you don't want the added weight of a dome piston, the heads can be shaved to reduce the combustion chamber size.

The 781 heads can be made to perform very well with some port and polish and increasing the valve sizes to 2.19/1.88

Thanks, I've built a few small blocks but nothing insane. I'm new to actually building a big block. Would you have any suggestions for a streetable 454 with the 781 heads? I'm trying to avoid stroking it cause I don't want to sink the extra money into it.

www.chevelles.com has quite a few combos of 454's in their performance section. I have one in my 66 El Camino but the only things done are a cam swap and intake so far. Haven't even driven the thing on the street yet lol.