[tdangle]

If you look up the HEI part number that came with your engine (probably 8917052) you'll find that it has roughly 22 degrees of mechanical advance and 20 degrees of vacuum advance. Setting initial timing much above 12 will cause total timing to be on the high side. You will need to somehow limit the total mechanical advance as to not go higher than ~32 degrees total. Vacuum advance is only in play at idle/cruise conditions. If you hook up a vac gauge inside the cab and watch it you'll see what I mean. Timing will not normally affect part throttle driving, only reduce total power or cause detonation if to high. Cars from the 70's had very low initial timing and ran well.

You may have a ignition misfire if you get shocked touching the dist. I'd look at that.

Speaking from experience: (i bought the SP350/357 deluxe) the Holley street avenger 670 is a horrible carb. I never could really get it to run will except at full throttle. I even took my truck to Westech (as on engine masters) and they didn't do much with with. Ran pig rich all the time. Now have a Edelbrock AVS2 which I've tuned with the help of a AFR meter.