I've been running billet alloy duals for many years now and find them better on the eye than Harley's offering. I also run a cool collar fitted to the oil filter too - all helps to keep the old girl cool when towing and looks pretty trick too.
I have run two oil coolers since having T-Man build my 117 in 2004. I run the same setup sold by Bob Wood although I made it up myself rather than pay Wood for the extra cooler and lines. I run a manual bypass on the second cooler so it can be bypassed in cooler weather. Works great.