"...I got a the engine strapped to the frame on the drivers side..."

That's the only way I know of to keep a stock type driver side mount from coming apart. If you have 500ft lbs of torque, and sticky tires that will hook, you must hold the ds down. I've used metal strap, chain, and turnbuckles. The '75-up "clamshell" mounts encased the rubber part with metal. So, it would take quite a bit to pull 'em apart. But, most all earlier style Pontiac mounts will come apart, on the ds, if enuff torque is applied.