speedo gear and ratio

[bjauto]

hi all as been  new to this game, i need help to work out my speedo gear!i have a 253 v8 motor and behind that i fitted a m20 Holden box 4 speed (one toner box) and my diff ratio is  2.78 and i'm running on 225/50/14 tyres ;what is the right speedo gear colour for this!!! i think the diff i fitted was for autos? allso my running combo will this be suitable or is the diff to tall at 1/1. ???