I think you'll find the tensioner was replaced with a positive action threaded tensioner. Whilst the factory is fine these are lighter and once locked in place wont/can't move. Basically its a bolt with two lock nuts. Adjust it set the lock nuts and forget it for a while. You need to periodicaly adjust the tensioner to take up belt strech.
These guys will avoid any potential problem as I've never heard of a tensioner problem
It's common practice to replace early Porsche tensioners with threaded assemblies as the original were prone to collapse and feed the valves into the pistons. $20,000 engine rebuilds were quite common in the 80's.