I have almost the same thing, 95 GMC Vandura 3500 with the 6.5L. I think Chev used G30 and GMC used 3500 for there 1 ton chassis designations.
In Wisconsin being 10,000lbs and under, if you leave over 50% of the seating in it is considered a passenger car similar to a suburban or passenger van. Your state may be similar.
If I had removed all the seats it would have been considered a 1 ton truck which in WI doubles the yearly tabs. Now that I have mine titled I am switching out the remaining seats and replacing with smaller coach seats on tracks. Then I can slide them out of the way for hauling. As long as I have 8 seat belts somewhere I should be fine.
When it came to both insurance and the DMV, I explained that I currently drive a suburban and would be using it just as I would that. For personal use only. Trips to Home Depot for supplies and transporting family and such. No commercial use needed to pointed out a few times.
I only put Liability insurance on it so that probably made it easier. I sold an old beater car to buy this so I didn't notice a change in cost.
Good luck with your purchase.