2518 with 13" tires

My 1997 2518 has 13" tires, presently the ST185/80R13 Load Range C size specified for the trailer. In my opinion, the tires are marginal at best for the weight of the trailer. The tires seem to bulge under load, even with no water in the storage tank.

My trailer has a "lift kit" installed.

I am considering either:

A) converting to ST185/80-13" Load Range D tires
B) converting the wheels to 14"

Load Range D - 13" tires have weight rating comparable to 14" radial tires. However, the 13" Load Range D tires will be Bias Ply tires.

Can anyone offer thoughts or advice on either approach, specifically does anyone know if 14" tires will fit in the wheel wells?

Thanks -- Brian