Bernie,
I think this is about it:
Create a new '68' driver in GPL similar as for other mods & close it down.
As Phil mentions, in GEM, Carsets -> add the 68GPL-EARLY to the active list.
Then select the new 68 driver & the 68 carset from both dropdowns.
In the available GEM options, select 60fpsv2newmod (& any other desired options)
Quit GEM to have it build the resulting gple68.exe
If you have nvidia profiles for your various GPL executables, also add similar for gple68.exe
EDIT:
When I initially did this, GEM seemed to be screwed relating to my 65 mod for some reason; just needed to run the 65 install again.
I think Phil also had some issues with 55 afterwards & had to install that again (although may not have been related/just coincidence?).
However, not aware of issues elsewhere.
Anyway, after you have 68 working - it may be as well to test other mods to be sure
Cheers,
Dave.