The Spal 4" fans will not fit behind the radiators with a Clark 3.6 gal tank installed. If you managed to wedge them between the two then you would have the fans rubbing against the tank and no airflow. With the stock tank they might fit down in the corners of the radiators, but they probably won't last as long being trapped between the radiator heat, engine heat, and exhaust heat.
If I rememeber correctly, the two fans together pull about 4.4 amps and the headlight pulls about 5 amps.
I wanted to get the amp draw close on fan start-up so I didn't keep surging the rectifier everytime I switched between them.
I don't know if Mt-Track will see this, but has anyone else run two of these on the front side of their radiators with success? I'm curious about prolonged use/abuse from rocks, crashes, cleaning, etc. I think this might be just the ticket for me to help with my cooling problems.