before everybody goes saying to get the Dak SGI-5 box listen up.

i currently have a 91Z28 (electronic driven speedo) 700R4 with 4.10 gears and the speedo was never fixed so of course its reading way faster than what i am doing. now i am swapping in my T56 next week and need to have everything ready by then. will the SGI-5 box fix all of this? will i need anything else? i would like to look at a correct speedo when the T56 is in.