Suburbans from '73 to '91 are the biggest rust buckets on the face of the earth. Look inside the wheelhouses, the lower door sections, rockers, around all the windows (windshield and quarter panels) and floor pans (pull the carpet).

A friend of mine had an '84 and there wasn't one panel that had not rotted thru.

If your roof has rust holes, I'd better there is more serious issues. You might want to try and find one in a dry area like Arizona, New Mexico or Texas.