Saw your thread on RamchargerCentral, and answered there, but you should be able to get a wrench on those bolt heads; I don't remember a "cap" on those bolt heads. It has a small plate under the two bolts, but mine did not had a bent-up keeper on the two bolts, on my '73. As I'd said over there, I'd put new mount bushings in, while it's out.
On the transmission crossmember, mine is a bolted-on situation, also, so I'm guessing that's a factory thing. How is the tailshaft mount? Mine was bad, and the engine/tranny had torqued towards the driver side, to the point that the tailshaft mount was vibrating a notch on the crossmember. I got a new mount, loosened everything up, and straightened the whole thing out. I still have vibration that starts around 42 mph, so something is still not right on mine. Stub shaft was balanced with the other 2 driveshafts, along with new Spicer u-joints, but I've read that it does not take much to get the stub shaft to cause vibration in these trucks.
My tail shaft was butchered like the rest of the install. The horizontal trans mount bolt wasn’t installed through the bushing that is surrounded by the rubber...it was installed through the rubber in a hole cut through under the bushing. Was hard to get the bolt out.
