I need ecm VSS info. My truck is a 68 GMC 1500 Long Bed . I'm running a 91 GM TBI 350 with a painless wire harness(both Chassis and EFI). my trans is an old Muncie SM318 3 speed 8 tooth drive gear on the output and a 20 tooth speedo gear. my axle ratio is a 3.07, im keeping my wheels 15". My Comp is 1227747 as requested by painless's instructions. my VSS is a 2 pulse made by JTR 2 wire (also specified per painless instructions). Im also planning on running Classic Instruments speedo(electric). The couple questions I have are painless want the VSS to connect to the ecm with the 2 pulse square wave sensor(directly). Classic instruments also need a signal from the VSS, but there is no ecm signal output to the speedo or vise versa the only output is in the speedo signal box but I think it changes values for the speedo output so I dont think I can use the same ouput for the speedo and ecm on their speedo box especially if the computer wants 2 pulse square wave. so my big question is can I tie the VSS wire and the speedo wire together at the output of there speedometer box or do I need dedicated wires? can I just tie the 2 together at the VSS? do I need a 4 wire DRAC to solve this problem? lastly being my trans was originally geared for a mechanical gauge cable drive i.e. 8 tooth output gear at trans, 20 tooth speedo gear; newer 90's gm trucks ran about a 40 tooth speedo gear in the 90's so how do I know that I will get the 2k pulse per mile? is there a calculation im lost??? who do I turn to to answer these questions, Im trying to keep this truck simple but its not going so swell. thanks in advance