Hi
Welcome to the forum
I presume you have a Citreon-Maserati box, which was used on early Lotus Esprits. This used a rod-shift design with a central shifter, so it would be worth searching some of the Lotus forums for info. Have a look at my build log, as I scratch built the linkage for my Renault box to give you a few more ideas.
Norfolk Tornado
Post some photos, so we can see what you've got & more people can then help out
Regards
Andy