Well, with no stock specs for the cam chain tensioner plunger, I attempted to make mine "to fit". Which meant assembling and disassembling a few times, and a few times in the lathe. Thank goodness I bought a self-centering chuck.
I started with the hollow brass slug that was the bodged part. I threaded it partway from the outboard side, relative to the engine. This way if the set screw were to back out, it would not fall into the engine. The set screw gave me a tunable platform for the inner-small spring to push against. I then proceeded to remove material from the slug until it got me an equilibrium on both springs. This way the tensioner could float properly as the chain moved. This was all hit-and-miss machining. I didn't even measure it in the end. I just took a little more off until it fit. I tuned the set screw in until I got the right travel on the springs.
The book said that the locking bolt should be tightened at the minimum position of the plunger. With that set, I buttoned it up.
The next task will be to try my hand at metal spinning in the lathe to make a suitable crankshaft oil slinger disk.