My rims are similar to Ridlers, they are Vision 142's 18x8.5 with 20mm offset. I wrapped them with 245-45-18's front and 275-40-18 rear. I have tons of clearance, could easily fit a 295 or 305 in the back but they would probably be too wide for an 8.5 inch rim.
You just need to pull on that lock linkage rod and it will release from the door. Pull towards the front of the vehicle. It's just a press fit in a plastic bushing. I had to pull pretty hard on mine the first time I removed it.
Its B5 blue, went back to the stock color. I just picked it up this spring after it had been sitting for about 20 years. Its just a basic 318/904. I put some 18's on it and a ralleye hood so far, then just painted it. I have some orange peel to buff out and then I'll post some more pics.