Speedometer inner cable to short...Model A

[GreatLakes28]

Bought a complete speedo cable, it broke. After purchasing an inner only, rebuilding the speedo head the replacement cable keeps sliding out of the head because the screw in is totally different. There is to much space from the boss to where the cable meets the retension part of the outer cable. I modified mine with a spacer, has anyone had the same issue? What did yoiu do to correct the problem?