I did similar with my Mamba Max Pro running tons of boost on a 6.5 in my B44. Didn't take the cells out but melted the wiring on the neg and on the link wire!
Can you set the speedo to 'blinky' mode with no timing at all and try it like that. Might be a bit 'driving miss daisy' compared with the current setup but if things still get hot then you might have fried the motor too. If it remains cool you can start adding the goodies on your speedo until you're happy
