I did not re-read all of the below threads. I know some of them apply
Use Of Flexane Urathene
Cheap engine shock mounts fix
Cheap engine shock mounts fix
Homemade Polyurethane Engine Mount Bushings
Homemade Polyurethane Engine Mounts - bushings
When the owner found out the cost of new shock mounts, they elected to (emergency repair) try Polyurethane Construction Adhesive "Liquid Nails" – No. LN-950.
The whole thread from below
380SL Diesel Conversion Project
Polyurethane filled motor mounts has shore hardness comparison chart
380SL Diesel Conversion Project
Mold making and casting stuff
Reynolds Advanced Materials | Everything for Mold Making & Casting