340 No low end power

340 + torker II + AVS + lean + low initial + 3" exhaust + not enough converter + high altitude = DOG!

Not too many thing working against you here. :)

High altitude can usually take more total advance than at sea level. Put a timing light on it and figure out the total and amount of advance in the distributor, which is easy math, total - initial. It may be able to handle 42-44 total depending on altitude. Make sure you rev the engine until it stops advancing, not some predetermined number.

I'd crank the initial up as far as it will go before kicking back on the starter, then figure how the current mechanical advance will play here. If you can add some initial, it may help your idle quality, especially if you don't know which cam you have. Purple shaft is a generic name covering the entire MP cam line, from box stock replacement to drag race grinds so that's no help on actual specs.

Sounds like the tune up may be off which will help get some of the low end back.

I'd put an RPM, LD340 or air gap on it if it were mine.

72-73 340's had 1.88 valve heads.