As long as the registration is not "to a business" or "commercial" then it's registered based on MSRP. It won't matter whether it's a 250/2500 or a 350/3500 model. All "private registrations" are based on MSRP.
You can look it up here to get an idea of what it will cost you:
https://dsvsesvc.sos.state.mi.us/TAP/_/ Click on the top row, far right section titled: CALCULATE FEES
Don't forget to check the "Recreation Passport block" !!!
That said, your insurance may be "dramatically different" between a 250/2500 and a 350/3500, so check with your insurance agent on costs. State Farm was the same (within pennies) when I last checked about a year ago.