440 wont start

I would take a look at the distributor cap. If you had it off it may have got some oil or something in it. Make sure it is squarely on the housing. Also make sure the rotor is on the shaft correctly and not cracked or damaged. I have seen people put caps on backward when replacing them, and the vehicle would still run to the point where the rotor had worn a hole thru the cap. Also, heads are heavy, so if you bumped the distributor with one, it is possible that you can bend the shaft. I had a small block Demon with the same symptoms, and sure enough the shaft was bent.