I am still trying to find out all the particulars with bolting a 273 intake onto a mid 70's 360. If all I have to do is ream out some bolt holes that will be no problem. No one seems to have a 100% clear answer so far.
I did nothing to the bolt holes on mine. No reaming, wobbling out or anything. I guess I didn't know they weren't supposed to fit. I used a very thick intake gasket though. A couple of them were kind of tricky to get started, they ended up fine. I used allen head bolts, not stock ones.