I was looking at my tires and how close they are to the UCA's. There's about 1/2" between the sidewall of my 275 series rubber and the balljoint end. Now 305's are about 1.2" wider than 275's. if you add .6" to each side to properly distrubute the tire width, then you would be hitting your control arms. Are guys putting 305's on stock 20's with no spacers? Here's a few pics of what i am talking about

 

Dog, when I had my 305/40/22s it was on a stock suspension and I never had any rubbing issues. Those tires measured 31.7" btw, the same at stock 20s as you know.

 

dogg ... the tire manufactures all very in true size. thats why some fit some dont bro

 

305's, stock 20s, zero problems. No spacers or anything else either.

The Coopers measure to exactly 31 inches tall.

 

I know it's not an issue on the torsion bar front 1500s, but I know there is about 1/2" less room on the coil over 4x4's. So I can't tell ya' for sure, bro...

 

Easy, you buy the tires, then get them mounted on the wheels. No, I have 305/50's, no issues but it is the absolute maximum width I would put on a 9" wide rim.