1990 KZ1000P rear cam guide and tensioner

I'm trying to resurrect a severely mistreated KZ1000P, model year 1990. I've managed to weed through previous wiring hackjobs to get it running, get all lights working, adjusted the valves, and now I'm trying to fix a noisy/loose cam chain.

The symptoms are a noisy clatter coming from the engine in the 1500-3000 rpm range. Other than the racket coming from the engine, it seems to run fine, at all rpms. I checked all three cam chain guides, and they seem to be in pretty good shape (although it's a bit difficult to check the lower two since I only had the valve cover off), and the chain stretch/wear is within specs. So everything seems to be in good shape, except the stock automatic cam chain tensioner is fully extended, and can't take up any more slack in the chain.

I looked through the tensioner installation hole and the backside of the rear cam chain guide appears to have an indentation or pocket in it, but then a metal insert in the center, to which the pushrod applies force. I'm wondering if the tensioner pushrod has somehow worn this hole or pocket into the back of the cam chain guide, exposing the metal insert inside?

But my main question for the forum is whether or not anyone knows how far the typical manual tensioners extend? I'm hopeful I can find a manual tensioner than can extend farther than the stock one (whic is roughly 60mm), so I can use a manual tensioner to push the rear guide in slightly farther, and possibly get away without having to pull the top end off the engine to replace the rear cam chain guide. Again, the main wear surfaces of the chain guides all seem fine, and the chain wear is within spec. I've included a pic of one of the lower cam guides, and the back of the rear guide, seen through the tensioner hole. Any input you can provide would be great.

No eBay APP ID and/or Cert ID defined in Kunena configurationYou might consider installing an APE (type) manual cam-chain adjuster, which may serve the situation well.
The contact point on the chain guide appears to be worn off-center in the image you posted. Not sure how that could be corrected with a different tensioner, but it may be worth a try before going through all the effort and expense involved with removing the head.