A few thoughts and Im sure I may be wrong, but doggy takeoff Id check timing, unburnt fuel at idle, after timing is set carb needs to be set at lean best idle,not turn the screws untill it is at best idle speed etc. there is a way to set /check timing and carb with a vacuum guage. The previous mentioned low compression may be an issue, but id make sure timing and carb idle is set then go from there.
problem with local mechanics is you dont know how into detail they are going to go with their checks, yeah its easy to blame the cam...but did they check and ajust the carb? or just leave it at a bench diagnosis that the cam is too big?
Think of it this way even with low compression the thing should run at an acceptable performance level. "Low compression" is a 318 hallmark and they run just fine. Id hook up a vacuum guage and see what it reads just for starters. The X heads are what they are, maybe 72 ccs, but many have put 360 heads on a 318 and most say they run real well...they are about 65 ccs. So yes you may lose compression but the car should still run enough to get moving from a stop. it may not do a top fuel burrn out though:)