The gooseneck is the best option. If you were planning to do any hauling in the future, consider buying a new 20'-24' goose for your own use! You can get one like this - 20' deck + 4' dovetail with 6' ramps, #6K axles with singles (gives you #12K GVW for the trailer + load - an easy haul with the 6400 on board!), 12-ply 16" trailer radials, electric brakes on both axles, spare, breakaway kit, I-beam construction on frame and neck with angle or C-channel on the crossmembers - ready to roll for between $4K - $5K, depending on where you buy it.

If not, you can rent one similar for a decent price.

I hauled a 1950 Dodge HHA 2-ton flatbed on my 18' car hauler (#7500 GVW, so I was overweight by about 500 lbs! (#8K!)), on 8-ply 15" bias trailer tires, and it pulled it like it was built for it. Any tandem single gooseneck will haul that 4100 just fine.

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