engine busting up

Pull the Holley, and rebuild it with decent parts. (I like AED kits..) If it did run well before and developed this, I agree it sounds like the carb. You have huge ports for that cam and compression, so carb tuning will be important to keep it happy. I dont think it's fuel flow. 4psi thru 5/16 line will handle things but only up to a point. You know the exh is bad, and the fuel delivery isnt up to snuff for more than a mild car. So you know what he needs to do with those. A cheap Holley Blue and regulator will fix the volume..Dont sweat the diameter, and plumb in a fuel pressure gage, and set the pressure to 8psi. That and the carb rebuild/tuning should bring it around. Also, what ignition box and ballast resistor is he running? The resistor should be .5 ohm or less (usually stamped on the back) and if the control box is orange, make sure it has a good clean solid ground to the engine, not just the fender or firewall. If you have a spare, try popping that in place too. those orange boxes can be problematic.