I am not quite convinced that adding a "remote" solenoid (ford type) really does solve the problem of standard starter/solenoid heat soak. If a starter does suffer from this build up of heat thereby increasing the resistance of its components, then to maintain 12 v, the battery must supply increased amperage to complete the start up process.
Just because you have a 600 CCA battery, the starter only requires 200 amps to work. Then what does the "remote" solenoid do to offset this? It still has to make a connection thru the heat soaked starter solenoid. GTO's do not have direct connect starters??
Minimum resistance for battery voltage/current to reach the starter solenoid is thru a fresh, clean, ample gauge wire connected directly to it. Other connections that interrupt that path just add to the resistance of the circuit. (Of course and equally grounded, minimal resistance bonded connection back to the negative side of the battery is mandatory.)
Using ohms law, and assuming: a. battery voltage = 12V, b. starting current = 200 amps. That means the over all circuit resistance is 0.06 ohm. (R=V/I 12/200 = 0.06 ohms). Not much resistance, for all practical results almost a dead short.
Another way to look at it is, how is the starter current limited with an increase of resistance? (I=V/R) 12 volts @ 0.06 ohms = 200 amps. Increase the resistance by just a tiny fraction to say 0.1 ohms @ 12 volts reduces it to 120 amps i.e. slower cranking.
The solution is to install either a heat shield on the starter or go to a newer style i.e. Robb Mc or similar type. These manufactures do not recommend using a jumper to the "S" terminal to eliminate the single wire from the ignition. (We all know that this is on paper and that a battery will drop below 12 volts during cranking on a "normal" mild day so the results of the math will change)
This is my reasoning/understanding, YMMV
Just an added note, on my 65, the alternator output has a wire that runs down to the starter and connects to the big lug making a connection via the big red wire to charge the battery.