Since he likes to go fishing, I would assume that a 4x4 would be a better vehicle for him. "Most" all 4x4 pickups that have a "manual" transfer case that has a neutral position, can be towed 4 down. Those without the neutral position typically cannot. "Most" all manual transmissioned pickups (4x2 or 4x4) typically can be towed 4 down.
So, visit car lots and ask to see only those with those two criteria. Then check the owner's manual for "recreational towing" and find out for sure.
Also, as mentioned above, you can always purchase and install a "drive shaft disconnect" device that will allow you to pull it 4 down.
Dolly's typically are for "front wheel drive" vehicles and almost all pickups (except the Honda) are rear wheel drive....therefore a dolly won't help.
We pulled our Toyota 4x4 pickup that was manual trans and manual transfer case for years and thousands of miles....just got tired of shifting those gears.
Good luck
Ron