[james schaechter]

The earlier model has narrower 3rd and 4th gears. They look similar to the casual observer, but many parts are hard to find. I would stay away from an early narrow gear as your main or only box.
Also, even if it is a newer wide gear box, make sure the input and ratios are what you want. It can get expensive changing stuff.
Yes, call Jerico and talk with Scott. If you can bring someone to look it over with you, better yet.
The only shifter to use is a Long Vertigate.