Mine had similar problems. Overheated sometimes, a lot of backfiring. I pulled out the aftermarket screen in the fuel tank outlet after I figured out there is a screen in the top of the fuel bowl. I suspected that junk was being pulled against the screen choking off the fuel flow. In the end it was the carb float level being set to low. Henry's filtering system seems to work well. I wound up getting a quarter bowl of junk in the bowl.
Try this site. Good info!
http://www.model-a.org/troubleshooting_chart.html