In deference to the vast experience available here I have a simple question. Which later model wheels offer the easiest solution for the 16 inch tire dilemma?

I think 907IE swingarm, wheels and brakes....

While this might be the simplest in terms of modifications required to accomplish,how hard is it to acquire wheels,brakes and a swing arm from a 907? I suspect it would be easier,for me anyway to add to my 906 swing arm than to find 907 parts at an affordable price. Also there a a lot of 900ss wheels to be had. I also suspect it will be easier to get michelin to make 16 inch tires than to find 907 parts. Are 907 parts truly a viable option these days?

i did the conversion and use a 5,5" rim, 180 tyre with the original swingarm.
the rims of the newer ducatis are compatible (750, 900, st2), the difference is the design, bearing, spacer inside the rim and brakedisk.

i had to machine the left eccentric and move the chain outward (ca. 5mm) to get a clear alignment of the wheels.

if i do the coversion today, may i choose the 4,5" rim or at least 170 tyre. the clearence is really less.

but the 180 looks good

There is a thread in the 750FAQ about making the change.