ever installed in turbo action shift kit? where does the plug go??

I found better instructions online for a later model 727/904 kit. The plug in question goes in with whatever valve sits next to the 1-2 and 2-3 shift valves in the valvebody pictured in the instructions, and is not present on my 904 valvebody. If installed in the 2-3 shift valve hole where it fits, it stops the 2-3 valve from moving at all, and I assume is the reason my 904 has not ever hit 3rd gear since rebuilding it many many years ago. Cheers All