"Right" was getting the sound from the "Line -In" loud and clear. I jumped the RCA's and probed the board, starting at the tape head (which sounded like "thpppp") and worked my way up the amp. That was after I installed the on/off switch for the amp. It also switches the jumpers from the RCA's. I added an "on" indicator LED so I wouldn't leave the amp on for days at a time.
The box still functions exactly as it should. Deck records from Line-In, Mics, and Radio just like bone stock. That was another part of the "right".
The only change visually is the switch and LED I added to the side panel. It killed me to cut a hole in it but the install came out super clean. The 3mm LED fit perfectly in the hole next to the Left Mic Input. The MOD is completely reversible, minus the hole cut for the switch. That's why I figured I'd apologize to the purists.
It was a real PITA without a schematic, but I was Hell-Bent.
I'm no tech by any stretch of the imagination, but I am very happy with the result.
Edit: The LED is next to the RIGHT Mic input. I'm anal about accuracy.