Ken,
The "R" terminal is only hot during crank, dead with the key "ON", and most of the newer Chevy starters no longer have the "R" terminal. Wiring instructions for non-point ignition tell us that the "R" terminal, if it's there, is not used. The instructions from Summit on replacement starters addresses the issues if you 1) have HEI/electronic ignition and an old starter or 2) are replacing an old starter on a points style distributor and need to keep that wire active -
https://static.summitracing.com/glob...um-829100a.pdf
Hoss, it sounds like you may be cranking with no voltage to your coil, then as you release the key to "RUN/ON" your ignition goes "HOT" and it lights off as it's coasting off the starter. You could check by disconnecting the Battery connection at the starter, putting a volt meter on your +coil feed and putting the key to "START". If you happen to have the old "R" terminal starter then a second wire to your coil + should fix your starting problem, but you need to check the voltage on that "stock Pinto HOT wire" to be sure it's not reduced voltage for the old points system. No "R" terminal? How about Summit's relay fix, plus verifying your stock Pinto HOT wire voltage?