Unless the van was running at moderate to high RPM when it came into deep water, I'd bet this is just an electronics issue, and a minor one at that. The air pickup on these vans is right below the passenger side headlight, so it is feasible that water could have been ingested. I would first pull the engine dipstick and see if there are coolant bubbles in the oil. This would indicate a problem. If you don't see any problem there, open the radiator reservoir and see if there is any oil mixed with the coolant. You probably won't see anything since the engine would have stopped immediately after potential damage occurred. The next step will be a compression check on all 8 cylinders. Anything over 100psi on each cylinder is "good enough". A compression tester is $50 and threads into the spark plug hole. You'll need to remove the passenger seat and the dog house inside the cab. Accessing the first 2 spark plugs on each side of the engine will be the hardest part. The rear 2 on each side are easy to get to from the back. Basically, you remove all 8 spark plugs at the same time, remove the gas supply and pull the electric fuel pump fuse (if it has one) or pull the fuel line from the inlet side of the engine block mounted mechanical fuel pump and plug it temporarily (the fuel line, not the pump). Install the compression test plug into the first spark plug hole, hook up the pressure gauge, and crank the engine over half a dozen times. Note the pressure on the gauge and write it down. Move on to the next cylinder and repeat for all 8. If you've got good compression than you've got an electrical issue which, on an engine that old, will only consist of the ignition system or possibly the fuel system if you've got an electric fuel pump. At this point you may want to find a garage that can sort those minor issues out for you.
If you find 1 or more cylinders that are under 100psi than chances are they will be down near 0 psi if you actually hydro locked. In this case, it may be best to find a decent used motor and a reputable shop to get the job done. As was mentioned previously, the sequence for removal isn't too bad. I have a '86 Econoline and removed my 6.9L diesel a few years back. If you paw through my build thread (link in my signature) there are a bunch of pictures of the engine removal process. I took a hell of a lot longer than 10 (or even 20) hours to do mine, but the 6.9L diesel is 2x the size of the 302, and I'm an amature. A good shop should have a 302 out and a new one back in with probably 2 days of work. 16 hours x $60/hr = $960 labor. A used engine and the required parts (new belts, hoses, filters, fuel lines) shouldn't run more than another $1000 at the most. If you had $2k in mind for a full replacement engine that will get you off safely and reliably than you'll probably have a little left over in the end. While they're in there, I'd have them do the front input seal on your transmission (assuming you have a C6), as the stock ones tend to leak if/when the transmission gets too warm.
And lastly, if you get this all sorted and find yourself headed toward Nova Scotia, look me up as I'll be on the way.
Very best of luck.
SG