Small Block to 904 Brace

you could drill one right through the brace hole and tap it, but you need a collar on the drill bit to keep from going too deep. you can run the bolt into the existing hole to find the correct depth and then back off from that a bit and use a shorter bolt. You don't need to thread it very deep because all the stress is to sheer across the bolt, not trying to pull the bolt out of the hole... I'd still use thread sealer on the bolt because the water jacket is there somewhere.