My guess would be that the second Harrison tank is a catch can for overflow from the first Harrison tank. Since the first Harrison tank is the fill point for the radiator, you have to have a second quart sized tank to catch any overflow.
The black tank on the firewall appears to be the catch can for the crankcase vapors at the valve covers.
The third catch can on the firewall is a little more puzzling. It has a line that looks like it goes to the intake manifold (?), not quite sure why? On the other sir of the tank is a black rubber line that goes down and could be collecting
oil from the transmission breather; that would be a requirement for racing. All points that could possibly expel fluids onto the race track need their own 1 quart catch can, not sure why the third tank has two lines into it.
I wish that I had a better picture of my catch cans for the Harrsion tank and crankcase, but it is too damn cold outside for me to go take one. In the picture attached you can see lines running from the Harrison tank and the valve covers to a point behind the passenger side front tire where the tanks are located. I put them where the battery box is and placed the battery in the passenger side footwell.
Interested in what others have to say.
Jim