Richie- I'm running a 3.55 rear, but I have 30x9.50 tires on the back, so our rpms are probably similar. I've played significantly with the timing, both total and initial, as well as the curve. It's been a while since I got it set, but I want to say initial is 15 degrees and total is 41. Any more than 15 initial and it didn't want to crank, more than 41 total and it would ping. Total timing in by 3000 rpm. I am still running points, so plug gap is set at .035. I would go up to .055 or so if I had electronic ignition. I run Autolite 45 plugs. If I did more highway driving I would go to 44s, or 43s if I could find them. As for the carb, I hooled my oxygen sensor to it for a precise reading, but you can get close the old fashioned way. with it fully warmed up, set the mixture screw to the highest idle speed or vacuum, either will do, then go in about 1/4 turn. I found my carb was jetted way fat, I was at 11.4:1 air fuel ratio when on the main jet, anything above 1500 rpm or so. I measured it with a drill bit, I think it was .058", then soldered it closed and drilled it out to .041 I believe. It took several tries to get it close to 14.7:1. Carbs don't run as precise as fuel injection, so it honestly runs between 14.5 and 15.3:1. Mine stumbles a bit on acceleration because my accelerator pump isn't working, so it causes me to drive like a grandma, but I'm ok with that in an old truck. I'll fix the pump someday.
Don't take any of my settings verbatim, it's been trial and error to get here, and may not work for your truck. I have probably 20 hours of tinkering and thousands of dollars in tools to get here. Find out what your engine likes and it will reward you.
Devin
