Since im gonna rebuilt my gsr tranny dude to the fucked up shyncros (3rd n 2nd) i was wondering what gear set i can swap out, but i definetly want my gsr 3rd gear set. you know how ppl put 5th gear set or 4th or 2nd, i wanna swap out my 2nd gear to a stronger one, but do you all recommend me getting and from what car can i get it from.

 

I think what you may be referring to is using the LS 5th gear in place of an ITR/GSR/SI 5th gear if you want it taller ONLY in that gear. Otherwise, I haven't heard of anyone replacing any other gears from other transmissions.