First I'd fix the dwell to 28-30 for single points or 32 for duel points. And then reset the timing. Gears 4.10 work great on those little 340's. And is it a 68-71 or a 72-.
I've got a white one also bought it in 88 and drove it that year and parked it in the corner of the barn. Guess where it's still at. lol at myself. I got a 340 for it and an 8 3/4. All I need is time and a little money.
I didn't see it was a 12 to 1 motor. Do as newbomb said on the plugs and don't be cheap on the fuel also. It's gonna cause a lot of damage if you are trying to use pump gas. I've got one car with a 12 to 1 with iron heads 340 and I pay for the 110 race fuel. And you can mix it up some. If you...
Well they lied to you. They used to sell n12y, n11y, n10y and n9y. Now they don;t sell the inbetween ones. So n11y would be one heat range colder. I've run all of the above in my 340's without issues although in the hotter motors I used n10 or n9. In my Hemi it was n63y's.