You're are either going to do to it correct, or you might as well not do it. Most all the rivets appeared to be in good shape, tight, straight, etc. There were a few that the heads had mostly rusted away. But how are you going to clean all the rust out that is behind the crossmembers? Or underneath brackets? Unless they are removed, you can't.
I may not have pulled wrenches as long as some on here, but I've done more than my share. And from what I've seen, there's a whole bunch of trucks and cars out there that were not riveted, but bolted. From reading the archives on here, I don't remember seeing anybody who regretted doing it. Just because you disagree with it, doesn't make it wrong. I see semi frames being drilled and bolts installed every day. I know this cause I sell them the mag drills and annular cutters to do it. Are they wrong?
I suppose I could have invested a couple thousand and gone back with rivets. And I could have. And then never use any of that equipment again. No logic there.
It's a done deal now, and I'm happy with it.
Mike