The 3/4 ton has a heavier frame and heavier suspension components. 8 lug axle hubs are needed to maintain the load capacity of the 3/4 ton.
If all you're hauling is a light boat and light loads, you don't have to have the 3/4 ton chassis. If you're wanting a 14 bolt axle, get one from a van that is a semi-floater. It should have six lug drums, but you have to be careful with the wheelbase width.
