I wasnt exactly sure where to post this so i thought the transmission section was the best place.

i want to install autometer gauges into my 89 firebird formula. it has a 700r4 transmission and stock 2.73 rear.

i understand the rest of the gauges but my main problem is the speedometer. i want to install an electric speedometer but what will i need to properly wire this up? can i just wire it to the stock gauges wiring or will i need this part? http://www.summitracing.com/parts/atm-5291/overview/

if that is the part i do need, will that mount directly to the transmission?