The easiest way would be to overdrill the hole a bit and tap it for a larger diameter screw. Problem is, you may already be overdrilled due to the helicoil repair. See what you can do on this score, you might be able to enlarge the holes in the gudgeons to take a larger diameter screw.



Other than that, installing a port behind the tramp would give you hand access to through-bolt it. Just make sure you seal things well.