Duck Stew,
Yes I do have own a 87 Paso. I actually own a 87 and an 88. I modified the 87 with the rear swingarm and wheel assembly off a 907 which means I run a 17 inch rear and a 16 inch front.
On the 88 I plan on putting the wheels off a 900SS CR which are 17 front and back with the stock Paso swingarm and front forks. I believe the 900SS CR is the bike I got the wheels off of. I had them powder coated black. I do need to have a new brake plate made to work with the smaller disk fitted to the 17" rear. I purchased some brake adapter plates and calipers to mount to the front forks but this is a work in progress and not at the top of my list. The SS wheels have huge rotors in front and a small one in back the Paso had equal size rotors front and back. The stock Paso front rotors are smaller than the SS but the rear is bigger than the SS.
Duck Stew if you have not seen the Paso Org site here is the link for everything Paso related
http://www.ducatipaso.org/I have the 87 here in Colorado and the 88 is in storage in NM. I am not sure what measurement you need but if you need one from the 88, I will have to get back to you. I know the 906 had the same 16 inch wheels as the 87. The 907 of course had 17s front and back. One more thing if you need tires for a 87 or 88 Paso or a 750 Sport or a 907 Shinko sells the original size tires for a very nice price. I doubt they are any where close to the quality of the original Pirellis and the Michelins but you can at least ride these wonderful bikes. I know these are not well thought of bikes but I really enjoy being a Paso owner.