Can you fit a GU box and pump as they are made genuine to go together.
Would possibly still have slow rev stall but at least it's a starting point.

sell what you have as working gq gear, probably worth more $$ not modified.
may find your left with something modified, no one wants.

GU pitman arm requires different tierod end.

when I got my new GQ T/R ends, local guy had pics with sizes ,so you may be able to get T/E localy that fits GQ drag link and GU pitman arm with out going to alot of bother obviously you need an adjustable link in the first place.

Think Superior or Snake Racing do this mod drag link as a ready part.
"GU one end and GQ the other".
Cheers