Need Tire help

[plumbers crack]

I need to put some tire and rims on my wifes Ford E350 van.
I want to put the largest size tire I can fit without lifting it.Current tire 255R7516.I would like 20 inch rim with 305 tire?

Is this possible?

[tblrklakemo]

should be fine....all depends on the wheel width and backspace. I am not familiar with the E van wheel wells, but if you stick with a 8-9in wide wheel and stock backspace you should clear them no prob.