Sure this tub is meant to come out more easily!
The spedometer cable runs through a hole by the left suspension. I cut a piece out towards the edge to allow the tub to be moved forward and free. If you don't you will have to dismount the cable at the wheel. Not easy.
Before re-installing the tub I installed pop-nuts in all the fastening holes in the chassis. Fastening the tub with screws makes it easy to remove if ever needed again.
I made a post about it when I installed stainless cooling pipes.