Vibration through body at low speed acceleration

Our car has developed a vibration during acceleration in around second or third gear. It is felt through the body almost as if it were coming from under the center arm rest or transfer case region. The vibration has a rubbery feel to it as if a rotating rubber part were striking the chassis/body. It occurs under light acceleration but I have not tried to push it by accelerating hard for fear of something snapping completely.

The rear suspension has been recently completely rebuilt with a four wheel alignment and front tire balancing upon completion. The rear differential mount bushing was also replaced. This gave us several months of improved road feel until this new issue occurred.

After some investigating I found a leaking left engine mount, which turned out to be completely destroyed. So both mounts have been replaced but the vibration persists.

Front guibo next?