Half Ton,
My expertise isn't that great - 3 years ago I bought an old pickup and began to search for what it would take to restore it or hotrod it. So I started with a complete tear-down of my 48 F1 and just this week it is officially on the road. I still have a bunch of odds and ends to finish, but that's what winter is for, right!? So take my advice with a grain of salt and a whole lot of common sense.

On the bracket bolts I'd say you're going the right direction. That's what I'd use. I followed a discussion recently about the merits of bolts versus rivets and here's what made the most sense:
Ford would have used bolts if they were cheaper than rivets.
Rodders have been using bolts as replacements for a long time with no problems.
Split lock washers and regular nuts will probably be all you'll need. Remember that the stress will be largely downward thru the cross section of the bolt rather than against the nuts.

I just did a similar replacement on radiator mounts on an 86 F150 and used bolts.

I am curious as to why you're removing the brackets - rust or relocation body parts?? Anyway, have fun. Easiest way I found was to attack them with the 4" grinder. - tim