I just changed mine on my 1965. The new urethane mounts were just too much vibration for me, replaced with "original equipment" rubber ones. They look a little more flimsy than original, but that is what YearOne has. Eliminating the vibration was a success.
I used two bottle jacks, poking up from underneath to find a flat, horizontal place on the front of the engine block, and one on the back. I had the whole car jacked up with floor jacks, and then used the bottle jacks to raise the engine. As suggested above, I did one side at a time, and moved my jacks from one side of the engine to the other. Not a lot of area for the jack, but it's flat enough to not slide off (always watch where your fingers are just in case). I had the trans mount bolts out, and took the long, motormount to frame bracket bolt out of only the side I was working on. Nothing else was disconnected and it only had to be jacked up 1/2" or so to remove the mount. The fan came very close to touching the shroud, but did not - I tried to position the fan to give the most distance possible. I figured it would be a long job, but really only took a couple of hours. Setting the jacks up properly probably took the most time.
And one more thing, the original motormount to engine bolts have a larger head than standard, making it a real pain (sometimes impossible) to use a socket. Next time I will probably replace the original bolts with some standard, grade 8 bolts so I can use a socket on all of them.