I just installed Michelin Defender in 275/65r18. Regarding that size: the measured tread width on the 275 Defender is the same as the 285 Dunlops per Tire Rack and per others who have measured. ...the tread width on the Defender seems slightly wider versus the total width compared with some other tires. Lots of 265 spec 10-10.4” wide tires on Tundra, Suburban etc, the 10.8” width of 275/65/18 will not be an issue with braking or other performance. I was concerned I would notice the narrower width but I don’t at all, 275/65r18 looks good on the truck, and the slightly taller (by 0.6”) sidewall looks better than stock to my eyes, although I might be the only one who would notice.
Have you got any pics of the 275/65/18 Defenders on your 200? Also, I assume you're on stock suspension?