72 302 Won't Start

After reading my earlier post, I jsut wanted to clarify that just because the engine might back fire does not mean that it slipped a gear. Any back fire is a timing issue. I guess the biggest difference is if when you make any adjustments thru the dist., the only thing that happens is a backfire.
It sounds like the timing may be a bit retarded. I think if you turn the dist clockwise, that will advance your initial timing. Just remember to make small adjustments, and you should be fine.

From here, it sounds more and more like your timing gear in fact has slipped. Do you know the history of the engine? Has it ever been replaced? If so, when and with what kind of gear set?
Stock nylon, stock metal, dual roller?
To make sure you have it on #1, remove the number 1 spark plug,and cover the hole with your thumb. Bump the motor until the air "puufs" your thumb. That's TDC #1. Your rotor should also be pointed at #1 at this time. The 'indicator/pointer' on your dampner should be in the range of 0-10 degree mark, depending on how your timing is set.

"IF" you are on #1 cyl, rotor at #1, pointer 'close' on the dampner, then timing MAY not be the problem.
Do you have a well charged (at least 14V) battery? Good tight clean connections at the starter and on the solenoid? On the battery? Could it be that your starter has worn out? Does it sound like the engine really.really has to work to turn over when you are trying to start it?

OMG!!!
800.00 for what!?!

A timing gear swap?? **** that! Go get the 200.00 sears tool box, a good 90.00 meter, and a 25. dollar chiltons and have at it!

Also, you can pull both valve covers, and turn the engine over to watch your rocker arms working. If the gear slipped, and valves hit heads, the rockers will not move consistantly, because you now have all un equal length PR's.
If that is the case, then you will need to buy a torque wrench, as the heads will have to come off. If that's the case, you may want to rethink what you want from the motor, and the car. Rebuilding iron heads is expensive for what you get. And, "while you are at it, now is the time for" performance parts.
Something to think about.

One question: Is the distributor rotor pointing at the #1 plug, or the #1 terminal on the distributor cap? Big difference here and seems to be a common mistake for the uninformed. It should be pointing at the #1 cap terminal. And do yourself a favor and get rid of the points ASAP. .017" is simply a starting point for points adjustment, you need a dwell meter to accurately set them. Which can be a big pain in the asss. Replace them with any of the electronic conversion modules and set it once, then forget they're there.

Depending on what comes with the rebuild, that might not be bad.
I still think you might be at least as well off just replacing the timing gear yourself...
Save up for a performance rebuild later if you want a "race" motor.....