Chris, the flange definitely does not seat on a machined area of the block. The machined area is just a circle around the main hole, does not extend out around the bolt hole.   I have a good photo but haven't been able to get it attached.   I can probably succeed with that tonight if it would be helpful to see it.  

I'm afraid I'll break it the next time I try to put it in also.... I did not pull hard on the wrench this time.  

This is the engine that came with the 77, my Dad bought it new in 1950.  Oil pump is original, unless the machine shop that worked on the block this spring switched it, which I doubt.

Thanks.

Tom