Without the yellow wire, I don't think the coil will have any power while cranking. I would have to test mine to see if that is true.
Anyway,
Russ mentioned adding a diode to connect to the yellow wire in the harness for systems that use a points distributor.
Here's more info from the Powermaster site:
http://www.powermastermotorsports.com/faq-starter.html>>>What do I do with the wire that went to the "R" terminal on the original starter?
In early original wiring harnesses, the "R" circuit was a ballast resistor bypass. This terminal is no connection when the starter is at rest, and is +12VDC while cranking.This circuit provided +12VDC to the ignition coil during cranking for easier engine starting.
Cars that do not have a ballast resistor (i.e. HEI, MSD, or other aftermarket ignition systems) should not need this connection. In most cases, this wire can be eliminated. If the engine has no ignition during cranking, then the wiring of the coil is going to require an "R" terminal signal. To accomplish this, connect a 3A/400PIV diode (or Powermaster part # 600 ) in line with the MOTOR SIDE of the solenoid. (Note: This is the terminal on the solenoid which has the cable from inside the starter motor connected to it. It is opposite the BATTERY terminal on the solenoid. The cathode or banded end of the diode goes away from the starter. This allows current to go from the starter to the coil and yet not from the coil to the starter.)<<<
You can buy the wire kit from Russ for $15,
Powermaster wire from Jegs for $22:
http://www.jegs.com/i/Powermaster/713/600/10002/-1?parentProductId=755522or buy the diode from Radio Shack, $1.99:
http://www.radioshack.com/product/index.jsp?productId=2062579BTW, A mini starter from Tom Telesco has the correct 3 wire solenoid, no diodes necessary!