A couple weeks ago, my distributor crapped out and the gearpin sheared off. I purchased a rebuilt distributor and have been trying to time the motor ever since without much success. She runs but it just isn't quite right. It surges under load and you can hear a couple slight backfires while driving. We located what we think is the timing mark on the flywheel, it appears to be and arrow, instead of a steel ball. Any suggestions would be appreciated!

1952 Chevy 3/4-Ton