I would recommend that you do loosen the rear mounts (as per the manual) and when you are putting the front mount assembly in place you might consider doing what I did by applying some gasket goo around the hole where the bolt from the motor goes thru the cover plate. This will keep oil from a leaking timing cover from weeping thru. There is a new motor mount available which is not rubber (I forget but think it is some type of poly) and it won't rot ever. If you contact me I can find the address.
Bill


1949 Chevy 1/2-Ton
"Sedgewick"
In the Gallery
1989 Caprice