The pedal can be sold here for a manual conversion, making a few bucks back.
Also get the clutch master cylinder and all the plumbing you can.
The down tubes won't fit right without working, and I personally would rather start from scratch if it were me.
As to the headers - that's a good conundrum. One thing -you ARE aware that the 5.0HO came standard with shorty headers as exhaust manifolds, right? I can provide pics of unmolested exhaust manifolds on a 91 5.0HO if you wish
The O2s - Bank 1 (passenger side) is in the down pipe, Bank 2 (driver's side) is in the exhaust manifold.
Grab the spindle out on both sides if you're thinking about going disc - or want spares.
If you like me need to rebuild parts and then replace them, grabbing the control arms (upper AND lower!) in the back may not be a bad idea. Also, the SC rear springs are at worst the same as yours, and if you don't have the JJJJ spring code, they're stiffer. If possible, if you don't have JJJJ, grab the front shock/spring combos.
For resell here, if it still has the ARC shocks on it, grab them out the back. If they're not bad, folks will buy them here and on SCCoA (albeit they don't exactly go screaming out the door ... )
The Tracloc will be a good addition, however, you'll want to regear it - it should be a 2.73 if it's a 5 speed SC, and that's a bit long legged for our 2 ton cars. But if your car is an open, it's a dandy core to rebuild with a 3.55 or 3.73 in it, and then do a quick swap.
Two more things - grab the seat belt setup - 'Murrikans are looking for them.
And for me, if it has the DRL module, I'd like one myself down here in Louisiana ...