It seems like always asking questions when trying to answer questions.
First, did you move the distributor any since you drove the unit last?
If so , you should use a timing light or get hold of one.
If you didn't move the dist and it is still backfiring , could be poor quality fuel, maybe moisture under the cap to name a few.This is where past history comes in because we don't know what the past was.
If you are going to get hold of a timing light, first clean the crank pulley so you can read the timing marks on the pulley. You should see the mark for TDC (top dead center) and some degree marks. Look for the 10 degree mark before top dead center and use a piece of chalk or white out, like everybody has white out, and mark the 10 degree mark.
Hook the timing light up to battery pos and neg and the heavier clamp goes over the #1plug wire as close to the plug as reasonably possible unplug the SPOUT connector at the ign module , start the engine and let it warm up idling if necessary and the 10 degree mark on the crank pulley should line up with the pointer over the pulley.If it does not line up , loosen the dist holdown bolt a little and rotate the dist a little in whichever direction to get the mark under the pointer, then lock the bolt down and don't forget to reconnect the spout connector and your timing is set.

Most important , be careful not to let anything get near moving parts when the engine is running , like wires from timing light or your hands, OK?
I forgot to ask if you removed the air cleaner assy from the front, which you can do to make the job a lot easier.

If someone worked on it prior, or an unknown,, might check for the correct firing order on the cap and for correct cylinder match.. Incorrect cabling/firing order will cause it to burp.

follow up
 

Thanks again for the info. I have not moved the distributor.

Sooo ,
Is this correct?
We have a vehicle that will now start and run, yes-no ?
If it does this much, what other problem(s) do we have ?
I'm "gettin ready to go campin". Got my stuff packed and all ! Am I going 1st class or am I going to have to pull this aux trailer with my garden tractor and go campin in some park where I have to get out by 5 AM? Tractor has no roof and neither does the trailer and my poncho is full of holes . Think you have problems ! Just kidding !
My wife offered to use her car and drop me off and she promised to pick me up, but she didn't say when.

follow up
 

Well, I finally got my RV running. One problem. As long as you spray carburetor cleaner in the intake hose, it runs very smooth. But when you stop the spray, it runs very rough as if 1-2 spark plugs are not firing. Put new gas in tank as none was left. Could this be an injector? Please advise.

Don't know how long this vehicle sat and it could have passed some water past the filter up to the injectors, don't know.
I believe there area few choices one of which would be to put some higher octane gas in the tank and if it is a clogged injector problem sometimes that will clean them out. The problem sometimes corrects itself the more you drive it.Another option would be to unplug each injector and look for one or two that will cause no change in idle RPM. If they are restricted unplugging them will not damage the converter. That might help pin down if they are clogged and at least which cyls are affected. Let us know what decide to try and if any change.

Thanks again. Will let you know when I check this.