Perkins 4-107 Engine Mounts

[Chasing Summer]

Rebuilding of my 4-107 is progressing nicely. New sleeves, pistons, and all that stuff. Also, cleaning up and repainting every part. Gonna be a shiny clean engine when I'm finished. Just how it runs as good as it looks. This is my first diesel overhaul ... little different than a motorcycle engine.

I have two sets of old Perkins mounts and a brand new set of Cushyfloat mounts.

Here's my question:
I need some pros and cons for each.
How long are 40 year old mounts good for? When I was in the Navy we wouldn't use anything rubber for more than 5 years.