What tonearm to drop-in replace Gray Micro Trak on Russco Cue Master?

[fillup_glass]

Just bought a nifty Russco cue master in amazing shape. Only problem is the Gray wood tonearm has lost its head. It looks like a 303 but not positive. Can't seem to find one and might as well replace the whole arm; not wild about the wood anyway. I expect there are a few drop in subs that would be suitable. I really like the Gray thick metal 108 arm but am more about pragmatic than perfect solutions. As you probably know, the mount holes are drilled into thick metal so it's important to keep the same footprint. Help, anyone?

 

[KentTeffeteller]

Shure M 232, Sedco, Audio-Technica ATP 12-T, Sparta.

 

[fillup_glass]

So my buddy I bought the Russco from found the Micro Trak 303 headshell. I slid it on the grooves but the headshell doesn't completely slide to the rear of the grooves on the arm. I don't want to force it. I've already pushed as hard as I care to. Is this amount of groove on the arm normal? I drew a yellow line at the end of the groove since it wasn't too clear.