cambelts aren't right for charger belts, wrong tooth profile as pete said.
You're barking up the wrong tree blaming the belts, loads of people (myself included) used toothed pullies with those HTD belts for years with no issues. I never had one snap on me, I just replaced them every couple of years as a service item. This was using the very first batch of pullies PSD got made up in about 2001/2002.
I'd suggest the pullies aren't properly lined up. Also, is the belt catching on the ARB mount? G40 ones have a small cut out in them for the belts but you might need to make this a bit bigger with the toothed belt.