Well, I made my own mounts so my installation doesn't have the inherent problems that have been encountered with jtr or msa or whatever, probably because the engine sits alittle higher, but I did the mounts with the headers on and then yanked the engine to weld it all.
1-5/8 may be fine for most mild motors, but it's been proven and well documented that big tubes, and as grump said, the "right collector" make gains especially in big motors and/or high rpm. IMO Don't plan on running 9's with small tube block huggers. IMO if your running 400 or more cubes and/or 7000 or more rpm, the 1-7/8 or larger are best suited. For that reason I'm going to build my son a set of 2 inch primary long tubes with a good collector.
As far as making another set or sets I can imagine it being rather expensive Mike, but Thaagard does that kind of thing, I'm just not set up to do that. Maybe you should just spend a week and come over, learn to tig weld and make some for yourself.