700r4 trannys

Hi all, new guy here.. Anybody profecient on 700r4's. Need to know about speedo transducer ( electronic). Basically want to know how many pulses per mile they put out. I'm talkin '89 700 here, from a 1/2 ton rear wheel drive p/u. I am puttin' it in a 57 with aftermarket gauges and need to know to set up the speedo. Appreciate any and all help. Thanks, Les