You can not use dry weight for much of anything. He needs to look at the GVWR on the trailer and see if that is under what the truck is rated to tow. Alos, with a 5er, estimate the pin weight at 20% of the trailer GVWR and make sure this is under the trucks rated payload or cargo carrying capacity.
This are estimates and you need to check real weights. The trucks towing and payload capacity are always based on a basic model (striped) truck, and one 150# driver. You need to reduce the ratings, bu options, accessories, tool boxes, hitch, passengers, 4-wheel drive and cab configuration.
If he gets a truck properly equipped, like a F35 woth the Tow Boss option, he might be OK, other wise he may need to step up to the F450/550 or the GM 4500/5500 series.
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