I was wondering, what displacements can a 305 be bored out to? I know boring it to 5.7 is dangerous but could the block handle something like 5.5l? Maybe 5.3l? And could the heads valves be bored to match? Just doing research lol

 

The block would have to be sonic checked to see how much meat you are working with but typically it can only handle an .030 overbore and sometimes a .040. Which makes it slightly less terrible than its original state. Don't do it unless you like watching money die.

 

You can get it to just a shade over 5.1 if you're lucky. Lots of em won't go that far .030" is about as far as they'll reliably go even when the block is in good shape (not all rusted inside the water jackets), which is just a shade under 5.1.

My advice: research something else if you're serious about what you get when you spend your money.