Which tires...? What size...?

[DamnYankee]

So I ordered a set of 18" Weld Renegade 8.5" wheels (I currently have 20" wheels with 275/45/R20 Goodyears).

Questions:

I would like to get as wide of a tire on the back as I can and maybe narrower on the front. Can you do that with rims that are the same size?

What tire size would I go with to maintain the same ride height as I currently have?

Which tire would be a good street tire giving traction for those "occasional" () times when I get on it on the street but still give a good ride and safety in wet conditions, etc? Was thinking of the BF Goodrich G Force T/A's on the back and something else on the front (same brand but something with better stopping ability)...

Help.