Buy the best you can afford make up your mind and stick with it, and most important, fast, reliable, cheap, you can only have 2, remember that.

I would rather worry about oil filtration before I worry about additional oil cooling. Oil filtration is the most important addition you can make, and that includes a stock rebuild.
Hope this

BTW my view of the perfect motor would be a 1835cc with thick walled cylinders, (same thickness of a 1500cc sleeve) single port heads, CW crank, single twin choke carb, with heating, oil filtration, doghouse cooling, Engle 100 cam everything else stock, 5400 rev max.