Technical Help I drilled into the coolant jacket!

Good to hear you used a dial gauge and turned the crank to see where you are. This is the only way to find out if your bellhouse is off or not. You could thread the bore and plug it with an insert. I would just find a place somewhere else on the bellhouse where you could drill a hole for a 1/4“ hardened pin.

 

I'd simply drain more coolant out to ensure it's below the level of the hole, and then spray the hole out with brake clean. Then mix up some JB Weld and put it in the hole first. Then after it sets up put some sealant on the dowel pin and tap it in place. Between the JB Weld and sealant on the pin it should never leak.
Don't try to drive the pin in before the JB Weld cures or it will just force the JB Weld into the coolant p***age.

 

Follow up;
Finally got it all back together. The pin still has a respectable interference fit, so I “slathered it in Loc***e” and sent it home. 200 miles and 10 or so heat cycles and it’s doing fine! No leaks.

Thanks guys.