Stock rim size of '89 F150

I just bought an '89 F150 to use primarily as a dump run truck. You don't get a heck of a lot for $500 but I'm pretty pleased with this one from a mechanical stand point. The brakes are being done now. It will have to sit in the drive-way so I'll have to clean it up a bit. Right now it has three different rims and four different tires. Since I won't get it back until mid-week I'm wondering if someone can give me an idea what rims will work size-wise. It is a stock long bed, 2WD 5.0 F150.