roughly how much movement is there horizontally on a sierra driveshaft? i need a set making up for honda diff with sierra outers but i have not got the car set up correctly (geometry wise) and suspension heights. how accurate do i need to be with measurements?

depends if push in or CV joint versions. Push (tripode) have internal springs that ensure the shaft stays central as its were throughout the suspension travel. a push in shaft off the car is longer than its intended fitted length

can't remember the exact plunge depths on the cv joints. What is worth bearing in mind though is that if you go for long spline shafts you can run them with circlips on one side only so the splines can slide through the joints. This is what the autograssers do, with shafts splined for 4" at each end. This is what I run on my Locost