If your diagnosis is correct my first thought would be throw out the old
plugs, just because they fire statically doesn't mean they're good and
they're already out, then look at the ignition module, they tend to be the
weak link in an old Mopar's ignition.
Then you add the fuel discharging from the carb. Normally a 318 timing chain is good for at least 150K miles. With the lower gearing of a motorhome the wear would no doubt be increased, so that could be a possibility. However it would take less time to check to see if the chain jumped than to write the post so why didn't you do that also? Also, have you done a compression check? That will certainly help confirm the chain.
I have a 318 Doge that was always a cold runner......... 85,000 and in a 1975 motor home...... Backed it up and when moving it , the motor stalled ( as usual for the cold running engine). Hasnt started since.....
Here is what I do know:
Will not start at ALL!
Rotor turns....ok so cam is turning.
Plugs all wet but fire.ok
No back fire whatso ever not a hint that it will run. just cranks and cranks.
Huge volume of gas vaporized air discharges out the carb. un burned.
Jumped timing chain?