Personally, if I had a M3W I'd be looking at swapping out the S&S and fitting a more mainstream Harley motor. There would be a bit of fabrication, but it can't be unsurmountable. Many Bike builders have swapped out the Harley engine for an X Wedge. There'd be a bit of faff with the electrics and ECU but again, all fixable.

The benefits of spares,tuning kit and dealer network would soon negate the initial hassle.

"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10