Section width on the M/T 325/50 is 13.1"
Section width on the M/T 28x13.5 is 13.2"
Section width on the M/T 28x12.5 is 12.6"
Section width on the Hoosier QTP 28x13.5 is 12.9"

Bias ply is going to flex more since the side wall is softer, so any of the 13.5's may rub. Sounds like you should go with the 12.5" tire to gain a little clearance. How much room do you have to the front of the wheel well? Bias ply will grow in height as well at speed. If you have 1/2 inch or more I wouldn't worry one bit.