350 timing how much

[Mertz]

I have a 350 in my 72 3/4 ton all stock except ceramic headers, edelbrock eps intake with edelbrock 1406 carb, MSD ignition and roller tip rockers.

I have had a problem with pinging pulling a 5000lb trailer in 95 degree heat. It also doesn't have the power to pull it up a 7% grade without some downshifting. I had the initial set at 12 and got 36 cent at 3000 and 56 with vacuum at 3000. I backed off the initial to 8 and am now at 32 cent and 50 but still have more that can come in above 3000. It is from 4 to 6 more at 3500. I am trying to tune the truck for the best gas mileage I can get but still have power to pull the trailer. I didn't have any pinging under normal conditions at 12. I have a blue and silver spring in the dizzy (lightest and one step up).

I think the ideal setup should be 12 initial, 36 with mechanical and 50 TT. Does anyone have any recommendation on the timing setup? I am on port vacuum but am considering going to manifold.