Like Kevin says, a stomp starter has no solenoid. You don't connect that purple wire to anything. But look at the other small wire at the R terminal of the solenoid in your new wiring diagram. That is the one that should connect between the post on the side of your soon to be purchased 12 volt stomp starter switch and coil+.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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