Well seeing as nothing else has been happening I decided to strip my spare gearbox today to see if my fear of a sad 5th gear were correct, unfortunately the were. Ill finishing washing it up in the morning and get a parts quote to see how crazy it will be to fix. Going to call marks adapters because I swear they used to make an upgrade kit with long splines on the mainshaft. But all I can find is gear ratio changes.
Also will call terrain tamer and see if there is any help there.