I'm replacing mine on my back in the driveway. I had trouble getting enough clearance to get the ole squashed mount out, and there was no way to get the new thicker mount in place. I thought that the motor had been jacked up as far as it would go and was hitting the cab. Duhhh...
I finally realized that the upper bracket for the mount unbolts from the bellhousing. It was hitting on the top of the frame rail, and that's why I couldn't get clearance. I started on the driver side, which has the pedals and the brake lines in the way. It would be pretty obvious, if you have a lift and good lighting.
Still, what I thought would be a one hour job has turned into a pain in the rear. First, the old mounts have to be chiseled off the brackets. After 60 years, they just don't want to leave. Very little room to work in there with a chisel and utility knife. Then, the new rubber mounts I got from Roberts are just oversized enough that they don't want to fit down into the hole in the bracket. I bought some longer bolts and hopefully the rubber will squeeze into the hole as I tighten it down. Maybe a little dishsoap would help.
The biggest problem is the rain that kicks up everytime I get started...But that's the thing. You come home from a frustrating day at work, and tackle an even more frustrating problem of your own choice.