I have poly mounts. Either way, the mounts shouldn't go, unless there is excess play. Put another way, if all your mounts are good and secure, they should be fine.
My dogbone is Rodney's adjustable one; the other mounts came from TFS. I was told that I wouldn't like the basically solid-mount result, but it's fine--if the motor is running smoothly. Smooth is really only an issue when stopped, though. Yours is a manual, so that shouldn't be a problem.