Jeff,
The main reason is that the rad (which is the same rad the motor has in the
original subaru), does not fit into the front of the standard.
I think a super has more room in the front.
Plus I wasn't sure if the waterpump would be strong enough to pump the coolant the extra distance.
It also seemed the easiest to build, at the time......
Mind you , I do have second thoughts. For instance I'm not too comfy having the rad with all the hot coolant behind me when I get hit from the side or something. But for now I'll go with it.
Rob.