We pull our 209 with a Toyota Highlander rated at 5000# towing which is the same drive line layout as the Exploder. I have not weighed the boat and trailer but it is all that the Highlander wants I estimate that boat and trailer are more then 4000#. At 75 mph you do not drive with your knee. I have never found a reason to use 4 low for pulling a boat up the ramp so don't get too wound up about that feature.
The 79 should not weigh anywhere near my 209 and I think the Exploder would be fine. I used to tow a lot with an old S-10 blazer. and it did the job fine.
Based on previous experience don't go with Pathfinder. it may be a true 4 wheel drive but when I yanked around the Nautique 206 it was always hitting the limits in the suspension.
If you can find an older Exploder they were rated at 8000# towing. Ford dropped that capability because less than 0.5% of owners used it.