Let me say from the onset that the following is not intended to demean Coker Tire Co., but only sharing my experience. When I restored my '54 Eureka landau, I bought a set of Coker 235-73-15 wide whitewall tires. They did not have an XL rating on them, but the sales associate felt comfortable that they would work satisfactorily on the (heavier) commercial chassis car. They did not. 3 of the 4 tires, one at a time, all during road trips, slipped a belt or otherwise got large sidewall bubbles that instantly caused bad tire balance and shaking of the car so you could not continue driving more than about 25 mph. I have since discontinued using the one "good" tire I have left.
At the time I was able to easily get the Firestone XL tires with wide whites, which have apparently been discontinued. I have since installed the correct 890-15 whitewall tires (from Coker) on my '54 and '60 Eurekas. The height difference has been discussed on the PCS site, and all findings mentioned there match my own. They have worked well on both these cars and I'm contemplating a set for my '53 Eureka flower car. Because of these change-outs I have stashed away the Firestones for future use.
Bottom line, I PERSONALLY would not use a radial without an XL rating on a commercial chassis vehicle.