OK. The mounts are in. LOL. What an adventure! So the key for me on the 4X4 4.2L was all the tips above.......BUT......what worked for me was to break free the old mounts first, and leave the passenger side in and do the drivers side first!
My mistake was going for the easy one on the passenger side first, and putting in the new GM passenger mount. It really should NOT make a difference, but it did for me. The height of that new mount on the passenger side simply would not allow me to torque the engine high enough on the drivers side!
I started this morning removing the new taller passenger mount and actually cutting a 4x4 just smaller than the old compressed mount, and laying it in between the passenger side mount brackets where the mount should go.. This was to make sure I could jack the drivers side, and allow the passenger side to fall to a lower height......and not break any metal.
I then moved my jack to as far as it would go on the drivers side of the oil pan and lifted, and sure enough, the engine torqued up on the drivers side and down on the passengers side, and the drivers side mount popped right out.
I had already ground down the new mount for the passenger side, (I put the nuts on and ground the top nipple off and about 3/8 off the bottom) and I decided to try that one, and it slipped right in! Don't mess with success!
I then lowered the jack and tightened the drivers side mount nuts, as I expected that now that mount would act to hold down the drivers side for when I moved the jack to as far as I could to the passengers side of the oil pan and jacked it.
Sigh. When I moved the jack and lifted, the engine did lift pretty well........but the NEW (not shortened) mount would not slip in! Its like the new mount on the drivers side was so tall, it was just enough to allow the passenger side to lift!
So I am not proud by this point to tell you that I whipped out the cutting wheel, ground off the nipple on top, and 3/8 of the bottom (again with the nuts on) and slipped that motor mount right in and tightened it up. I used blue thread lock on both sides.
The main thing was watching all the videos you could and THIS forum. I got the trick about moving the jack from side to side and a little grinding from one of the other motor mound threads, as well as the tip about doing the drivers side first with the old compressed mount still in the passengers side.
Another thing for me was removing both front wheels, and putting the car on jackstands just a little higher than the car would sit with the wheels on. I was able to get to the bottom and top nuts with my Frankenstein compellation of universal joints and wobble extensions, and even use an impact tool to break them loose at that height. I used a small step ladder to reach in on the top. The slight jacking and wheels out of the way also allowed me to find every nook and cranny I could reach into from underneath to work on this situation.