Check the registration laws of your particular state, and ask your insurance agent about the insurance.
My F350 cab/chassis required a $1M commercial policy, which cost about double what my F350 pickup cost to insure with $300K limit. This was for a '97 F350 4x4 diesel dually cab/chassis 11,000 GVWR, versus a '92 F350 4x4 gas single wheel pickup 9200 GVWR, both with the same insurance company, same driver, same location, same full coverage comprehensive, etc, except the commercial policy did not offer roadside assistance, which the pickup policy did.
Once you do get a commercial truck policy though, the price doesn't change much from one commercial truck to another. My International cab/chassis doesn't cost much more to insure than my F350 cab/chassis did, while the International is newer and worth twice as much as the F350 was and the GVWR is 3 times higher than the F350's (11,000 vs 33,000).