I'm working on the updated manual as we speak.
Folger Tech is working on multiple projects at once and I am involved in most of them so I have been juggling a lot at once while remodeling my workshop to make space for them.
Overview: The original i3 Mega kit shipped with the same M5 threaded rod as the 2020 i3 kit does. We decided to upgrade it to use T8 Lead Screws soon after it was released. Sometime in October 2018, kits started shipping with the upgrades included. Due to being so busy at the time, I was unable to update the manual in time.
Here I will show basic images of the changes. It should be pretty simple for users to figure out what needs to be done.
There is a 6mm Acrylic spacer that needs to be used on the SK8s. There is also a T8 nut bolted into each of the X ends as shown here:
There is a new z rod holder with an offset for the new Z rod location as shown here:
Pretty much everything else is the same.
Ask below if you have any questions. When the updated manual is released, I will lock this topic.