My concern would be the initial slip of the wheels then the grab of the locker. With a heavy truck, camper and boat in tow, I think the Gov-Lock might fail. The shock of it locking up could break the the locker or even an axle shaft.
If you are going to the trouble of tearing into the rear end (the 14 bolt FF's are one of the easier axles to set-up), pop for the extra control of the Eaton E-Locker. Flip of a switch and the axles are locked. No slip, no bang, and less of a chance of breaking an axle or anything else with proper operation. Lock it in as you back into the water and unlock it before you make any turns.
John is right about winter operations though. The Gov Lock works well because its only working when your stuck. A locked rear axle on slippery surfaces make a moving truck slide sideways very easily. The Gov is less likely to do that.
2012 Chevy 2500HD ECSB, 6.0L gas, auto, 4x4, LT
2003 F450, 7.3L PSD, 6 spd stick, 2wd, dump truck
1983 GMC K2500 pickup - working on a Cummins 5.9L swap
1987 GMC K3500 Dump, 6.2L diesel, TH400 auto - project plow truck