Projects Drilling iron case saginaw 3 speed

Hey guys im doing work on my buddys c10. Has a 230 with the saginaw 3 speed and im fabricating a new trans crossmember. The truck had the side mounts on the bellhousing but we need to relocate the mount to the tail of the trans, the tailhousing has the mounting "pad" cast into it, but the holes arent there to bolt a mount to. Will i have any issues drilling the cast ? Should i tap the holes or just run a through bolt ?

 

You can do either but back side of mount flange must be reasonably flat for bolts...

 

Factory drills thru & threads the holes ... tap would be 7/16 NC as I recall.

 

Thanks guys, ive seen the exact same tailhousing with the holes drilled. The back side will work fine. Ive never drilles cast before, didnt know if cracking could be an issue

 

Not many guys looking for that trans any more; you can probably find a tail housing already drilled/tapped to swap.
I am Butch/56sedandelivery.

 

Hes actually planning to swap the engine and trans out this fall and were on a tight schedule so were just trying to make it work with what we have.

 

It's most likely going to drill like butter. More like drilling a hokey puck.
Keeping it straight will be the challange. Drill a pilot hole, follow that up to size

 

Tapped is preferable, as holding a nut while undoing a bolt is always a hassle.
There are transfer punches made to locate the holes accurately, and drilling and tapping square is very important.