Frickin' timing chain
Keep in mind that any tensioner will reduce timing variations, but it won't remove and retarding of the cam timing due to a stretched or worn chain. The tensioner will just make the cam timing steadily retarded.
If getting the car to move under it's own power is the sole goal, then any chain will work. The OP can decide if that is all he wants, or if he wants a better chain for long term use in the 318.
IMHO, it would still be a good idea to pull the distributor, prop a mirror and light up to view the top of the intermediate shaft while standing at the front of the car, and turn the crank and look for the same looseness, crank to shaft gear.