OK....Update.
Plugs are Champion C59YC. Rick Parker told me that he saw them on the chart...they're next to the lowest for being cold.
Put a regulator on the fuel line. Running at 6 psi now.
Got another problem now....I mentioned it in another post....Alternator pulley is too big to let the alternator charge at idle. Battery has basically been getting drained (down to 56% according to my battery charger) while idling and low throttle operation....i.e. tuning carb....checking for fuel leaks, etc. MSD hasn't had enough spark to thoroughly make things happen efficiently...so I had a little miss and now the plugs are sooty.
So now I have to see if I can find a smaller pulley so the battery will charge 24-7. Will probably change plugs now.....so just wondering if I should buy a hotter plug while I'm at it.