2WD...4W alignment???

It's a '96 ranger 2wd 5-speed, the rear tires are wearing real bad on the inside. I was told I cant get a four wheel alignment on a 2wd, they only do four wheel alignments on cars. But I know a guy who said he had a four wheel alignment on an f250 4wd. Does 2wd and 4wd make a difference?who's got the answers? my tires wear badly.