a pan will work just fine but if your staying with a 72 frame you might as well stick with a 72 shovelhead.
a belt primary will do away with most of the shovel oil leak problems.
if you want a smooth running engine use the stock 74" flywheels with big bore(3 5/8) jugs. that will make it an 82".
or an 88" with the 1340 cc flywheels & BB jugs is still pretty smooth.
I wouldnt recommend going over 93" (3 5/8x4 1/2) for an every day rider with harley cases because the vibration will cause loose & broken bolts & stock parts like push rod tubes, intake manifolds, oil lines etc. will no longer fit.
with after market cases the skys the limit on size but your going to have to live with the vibration.
ryde on's right, a 93" s&s is your best bet for appearance & reliability.
my current rider is a 96" solid lifter shovel I built up with stock bored out cases 4 or 5 years ago & adjusting the pushrods & drilling & safety wiring bolt heads just aint near as much fun as it used to be. I expect you'll feel the same way about those struts in a few years, dont throw away those shocks. you may need them later on.