The radiator that fits that shroud your showing is off a standard k75, K75S, or K75C and T.. it's physically smaller in dimension and unless your good at fab work, prolly a radiator from that series would be easiest.....Also, you'll need to fab up mount points for the front of said shroud to the front of the fuel tank.....kinda like this here.. the RT tank doesn't have those little round stock rods with rubber pads as the K standard and K75c do. If you decide to "go to a different tank" approach, then be wary of the side panel mount point tabs on the rear of your current tank...or you could just go the low seat route with the tank surround....A lot of the older tanks you see on Ebay etc (as this example shows), don't have those rear mount tabs on the tank...
I'm doing this EXACT thing right now...but I'm not into the tear down stage , yet...just collecting parts.....