Re: How to drill a sbc heater box cover and make it a bbc heater box c
I have not. If my car wasn't a "numbers" car, I would have drilled it and converted to big block heater core when I had the car apart. This is one of those INSANE things that GM did back in the 60's. Why wouldn't they just use the same cover for big and small block? Would have been less part numbers, and easier. The big block heater cores are even easier to swap out when one goes bad.
But, back to your question. Can you buy just that little plate that bolts on the BB heater box cover? If so, I would buy one of those, position it on the cover comparing to a pic of the BB cover and get out the hole saws. Someone somewhere has probably posted a template. I am certain someone on here has a BB that is under construction, and would be glad to take some careful measurements for you.