If your keeping aluminums , bolt on spacers might be the only alternative to larger tires , may be able to fit 235/85r16`s if you have room to loose 1" between, check the concentric part of the hub on the dually dana 80 axle ,it steps down so there`s only about an inch that's fully available to capture the rims , meaning you cant use slip on spacers ,I used 1/4" spacers on my 99` Dodge dually W/ 17" steel rims from an 04 up truck w/ 255/80r17 tires , handling
was fine w/ TC
Some tire shops wont mount tires rated for rims that are smaller than in specs
Bolt on spacers will make it harder to use the TC , to wide to load