Foward shift to top shift conversion ??

[RunnerRick]

I have everything for my dual cases but I can't find a top shift.  My truck is forward shifting and I have two other forward shifting t-cases, can I convert to top shift and if so how and how much.

[RunnerRick]

Found the kit on marlin, but don't know what year the cases are. Also if someone knows what I need for a shifter.