Anyone know how wide a tire and/or wheel I could do on the front of my 88?

Well that's somewhat promising I guess. Thanks.

Anyone know how much clearance is needed between the sidewall and fork?

I don't use the front fender, Haha

I plan on going down to a 16" wheel and putting a nice chunky tire on there

I can tell you what doesn't fit. I tried the 5.00-16 lightning tread Arco tire (in modern that is a 130/90-16) on a mechanical drum star hub 1957 Harley wheel off my Panhead. Forks are too narrow for that old of a wheel/brake combo. Tire would not clear the front fender mounting nubs.

I've got a 1969 GT750 Suzuki drum wheel here with a 90/90-19 tire on it that mounts beautifully, looks killer and actually improved the braking and handling of my 98. State patrol messing with me forced me to reinstall the front fender and disc brake front end. So that wheel is going on my 1963 Honda, which doesn't need to have ANY safety crap other than a left hand mirror, a taillight and a headlight.  

Having ridden many a custom over the years, I'll warn you that 16" front wheels look nice, but make the bike handle like s***. Tall and narrow fronts are the way to go. I've got a steel plated shoulder and a clutch lever through the lower jaw scar  to attest to that.

The 110/90-19 (Dunlop) gives a fatter look.  It will fit easily between the forks, but the fender will have to be raised a few millimeters by elongating the 4 screw holes that attach it to the fork.  I've run the tread off of one tire and am getting a new one this week.

Pretty sure trukinduck put a big tire on front, but his bike is heavily modified. Might try searching him. Not sure I spelled his name right.