Help with 14" or 15" tire decision

I recently acquired my first Trailmanor, a 2004 2720SD with 14'' wheels and installed lift kit. I want to replace the tires. Especially after combing through the forum educating myself on the tire issues. The current tires/wheels are S/T 215/75R14 with 14" 1870# rated rims. The question is do I go with the 14" Kumhos or the 15" Maxxis. Does this sound familiar?

From what I have gleaned, I will have to buy new wheels to run either tire. I do not expect to run heavy or drive at more than 55-60 MPH, but with the price difference minor, the smart move is to upgrade to 15" tire. I can deal with the spare tire modifications. The real question is will they fit.

I have four inches of clearance over the top of the tire to the wheel well right now. This obviously exceeds the recommended three inches. But, the clearence on the curbside to the rear is only 2.5 inches. The attached photo shows the tire is closer to the rear in the wheel well than the front. The 15'' tire would have a diameter of 28.3 inches vs. 27 inches for the 14''.

Can I get advice on whether this provides enough clearance for the wheel travel ? Seems like it may be cutting it close over a bump. Any help is appreciated for a first time post. Thanks.