Welcome to our little group, Steve. Listen to Gordon, here- 16" wheels with 6's or 7's on the front and 8's on the back. For tires, 195/55- 16's (24.3" tall) or 205/50's (24") would be good choices for the front, as either will fill the wheelwell, are more than enough tire (for handling) and anything wider will be too heavy for the suspension to control properly (not to mention slightly heavier steering and I would think faster wear on parts, as the elves at Wolfsburg simply never envisioned their design ever dealing with all that weight). On the back, 225/50's (24.7" tall) on 7's or (preferably) 8's, or 245/45's on 8's would look great.
The sizes for the front are a touch short for accurate speedometer reading (kind of a misnomer here, as we are talking about VW speedos, and they are anything but accurate!
) but I'm not sure anything much taller wouldn't have clearance issues. Going too much taller on the back (from the stock 25" tall tire) will make the overall gear ratios taller and you may not like what it does to acceleration, as well as making it harder to keep the car 'low to the ground'. 9" rims with the 245's would be really cool, but I think backspacing/offset would have to be 'just right'. I don't know if anybody here has done 9's on the back of their flared tub.
I'm a fan of Fuchs alloys on Speedsters, so of course I think 16's would make your car look bitchen', but that's only my opinion. As nice as the wheels Banzai (sorry, Banzai, don't know your first name) has, it's hard to get anything that wide in 15" tires any more, and I think his combo (6's and 7's) are more suited to a classic bodied Speedster. His 7's have the extra width to the inside (a la the uber rare and ultra expensive 911R rear wheels), which may sit the wheel/tire too far inside the wheelwell for your taste. Great way to get a wider tire on the back of a regular Speedster, though. I'm surprised there hasn't been more interest.
Hope this helps. Al
PS- As for Gordon's taking off the 225's and putting 205's all around (so he can rotate the tires- really?) This is potentially a fine, high performance machine!
Gordon-
You're a Poopiehead!
(it never gets old!)