Hi guys,
I just thought I'd post this for any first gen Avalon owners looking for info on wheel/rims fitment. I just put a set of 18" rims and rubber on my 1996 Avalon and they fit perfect! Here are the specs:
18" (used) TSW Catalunya Hyper Black, Chrome lip. 8" wide, +20 offset. Bolt pattern 5x114.
225/40/r18 rubber (used, multiple brands)
I have not had any issues with rubbing, and have a relatively small gap between the wheel well and tires (2" maybe a bit more).
(I've got to brag here a bit) Total cost = $525 CDN!

($225 for all 4 rims, $300 for the rubber)
I would recommend to anyone looking to put rims on their 1st gen Avalon to go with 18" (maybe 19"), nothing bigger unless they want an added expense (and headache) of other modifications. 18" really fit the look of the car well, not overpowering, and not too small either.
Will post some pics of the rims installed as soon as this overcast weather clears up!

-Matt