Posted once before but need suggestions

You didn't say, but i'm assuming your '72 /6 is in a '72 body,in which case check out the
mech parts 4 sale. dartman65 had/has an excellent JR/hedman 6 into 1 MP header for
sale, may not make as much ultimate HP as 6 into 2 into1 will,but more than enuff 4 your
goals. rusty's rite & if you insist on dual TP's split 'em out back. 318 carb on supersix
intake is fine if you re-jet accordingly,non-feedback holley if poss.
If you were willing to pull the head, milling the surface .060, and getting a fresh valve
job back cutting the valves will pretty much be the most bang for the buck w/o getting
into expensive stuff.(cams, OS valves & springs,porting etc.).
the /6 bore is small, & plug location decent, so the bump in comp. ratio won't be an issue
& worth steppin up some octane for. :)

PS if you do the head mill & or valve job don't forget to back off your rocker screws 1 1/2 turns B4 re-installing the rocker shaft! Cheers!