This car is awesome, the "custom flares" and other sweet period modifications! Awesome that it has a hotrod MFI engine already sorted out. Followed the BAT experience, nice purchase. I'm obviously a minority but my favorite tail of all time is the one your car currently has and it works with the flares IMHO vs. on a stock narrow body car. Following for sure.
Bright trim vs black: I don't know nearly as much as others on this forum, though I believe there are some factory subtleties on the '73 that differed from earlier LWB cars such as: black trim around the signal and tail lights, black horn grilles, black rear grill (also '72?), bright window trim, bright flag mirrors and I think still bright headlight trim? To the "expert", some of these these give the car away as uniquely a '73! Just another thought to consider, originality is long gone in a good way so none of it really matters...
I 100% agree the current mirrors need to go, drive it!