What do you want the shift kit to do? Why can't you just shift it manually ? You Know: Pull it into LO, wind it til the valves float; move the lever into DR (2nd) and as soon as the transmission shifts, yank it back into LO which will hold second. Wind it til the valves float and move the lever back into DR and it will shift into 3rd. (the floating of the valves is optional).
I think there is a shop in Georgia that will go through a FOM and make it start out in first like a FMX,I thought I had the info but cant find it right now but if I find the info will post it.
1955 Furdomatics were 1st year to be able to start in 1st gear while in DR. If you stomp on the gas at a stop the trans will start in 1st gear, then shift up to 2nd and 3rd. You can play with the TV rod length a little and get this affect too, but don't shorten up the rod too much as the trans will start in 1st even with little throttle opening. You might find an FMX shift kit that might work a little.