Well, I've ordered the parts I need to complete this relatively simple modification.
After some careful analysis of the structure, suspension, subframe and the 3 other engine mounts, I truly believe that no real harm can happen. If anything, it will be safer by not relying on the oil filled internal shock absorber from failing and coming apart. This new mount will isolate the vibration well enough.....vibration will not be transmitted through the stock rubber subframe bushings....in fact the subframe will be taking some of the torque so there should be a significant improvement in reaction forces. Most importantly a lot less engine rock with subsequent flexing of intake, exhaust, hoses and wiring.
That stock rubber isolator is huge and must weight 5 lbs. It measures 3 5/8" f/f but it is easily compressed by hand and if you grab the bolt studs on either end you can bend one, the piston shock absorber end. When the engine is resting on the mount it compressed about 1/4" at rest. The motor is balanced with supports very well. One on each side, one and the rear and the big one up front that is the damper in this classic engineering example of a mass, spring, damper system. This system is used in our cars to give them that "you can't feel it shifting" comfort and cushion the torque transfer during abrupt changes in thrust in either direction.
The braking forces are dampened by the subframe bushings, so they will be more than adequate to withstand the acceleration forces.
The mounting bracket for the engine that attaches to the front mount is massive cast steel that weighs almost 4 lbs as well. I'm not going to change that one, it'* a very good strong design.
I am going to make up a spacer disc out of aluminum structural bar stock 3" diameter, following the basic outline that rround gave me. Kudos to Rod.
On either end will sandwich a 3/4" urethane waffer.
Keep you posted but work is busy so I won't be doing much until the weekend.