On a combo like this, i'm getting a MSD Mech. dist. with a Mallory 6AL box, it does not have vacuum advance, it is primarily a street car, what would be a good baseline for this combo?

71 dart. Manual steering & brakes.
360 magnum, stock short block.
RHS heads.
9.1
Re-ground stock cam 1.6 rockers. (.477/.477, .218/.218 @50, 112 LSA)
Summit headers.
RPM airgap, 750 3310
904, PTC 2800 11", 3.73 gears.
MT 255/60/15s

Something like 15 initial and 35 total should work. Have the advance all in by 3500 rpm. Try that as a starting point and see how it goes.

What Andy said is pretty close to what my 360 runs as well. Its a little beefier than yours but even when it was milder about 15-16 intial and 33-35 total all in by 3000 rpm is what I've run with success over the years. Hope that helps!

I would set the initial to what your cam/eng wants then shorten/adj the total to keep the aforementioned 35 (vac adv disconnected/hose plugged if VA is used)then play w the springs (and definitely toss the stock heavy one w the long loop) going as light as possible staying JUST UNDER the pinging point as you run thru the gears at WOT. Then if vac adv is used plug in the hose and work w it for the most adv also wo pinging at PART throttle like at a steady cruise on the highway and a high enough RPM where the mech springs are maxed out. done in order on your hottest/driest day (most likely to ping).

I set it up for 20* of advance (14 int. 34 total) all in at 2400 (lightest springs), it seems to be working good.

pretty close to mine.
i use 15 initial and 34 total all in by 3200.
i'm running 10.3cr.
with 9.0 you'll have more flexibility with timing settings.