355 Couple of Q's on muffler/cats R&R and Y-pipe rattle

My '98 has a Fabspeed muffler and stock (ceramic core) cats, and I'm swapping in aftermarket cats and stock muffler. (BTW, if anyone wants the Fabspeed muffler, please PM me, it's perfect and has 240 miles on it, installed by the PO, and genuinely sounds good -- I just prefer the stock sound).

Anyway --

1. Should I be removing the rear wheels for better access to the forward bolts on the cats, where they join the headers? I'm a pretty experienced wrench but man these are a godawful PITA. I have them all out now but can't imagine how I'm gonna get them back in given the limited access. Seems like I'll be tightening them 1/8th turn at a time. Any tips on this greatly appreciated.

2. I really want to do a test run of the system before I button everything back up and align the muffler to make sure all the joints are properly sealed. Any tips on this? Eyeballing it right now, it looks like the angle the cats sit at will decide where the muffler sits and whether the tips are centered in the bumper. Feels like a catch-22, if I tighten everything up to check for leaks, after I install the bumper I'll have to loosen it all up to align the tips. Do people just install the bumper, align the tips, and hope for no leaks? And if you have leaks, remove the bumper and start all over?

3. I thought I had a bypass valve rattle but upon getting everything apart I'm very pleased to discover my car has a Capristo valve and that the right side Y-pipe tinwork is loose and must be the rattle culprit. It looks loosest at the front, so I was going to un-fold the tinwork seam and using channel locks pinch it tighter on the pipe, then fold the seam back over. Anyone have a better idea?

Thanks for any guidance here.

 

Coupla pics just for fun
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Thanks -- have the CV boot shields removed. Will give removing rear wheels a shot. It's the outboard cat to header bolts that I'm finding just brutally inaccessible.