Dead axle length

This is what the service manual shows...no + or -.
Also straight within 1/8"

If the outer holders were tight on their tapers they are likely okay. Just be sure when assembling you can get them locked on good and then wiggle the sprocket a bit before tightening the preload adjustment. I have seen aftermarket sprocket hubs and outer holders that would interfere and not allow the holders to lock onto the axles.
Later Bob

Definitely do not put a spacer behind the inner bearing, the difference in lengths can probably be accommodated by the bearing pre-load adjuster in the outer hub. Its likely that the shorter measurement is the incorrect one because some clever person pulled the sprocket against the end of the shaft rather than using the correct spacers and pulling against the hub. If you can get the adjuster right back and the outer hub will tighten on the shaft, it will probably be OK, The problem will come in lining up the track frame, you may find the dowels are not long enough to hold enough shims. Pull the dowels out and only tap them in a short distance leaving enough out to carry the shims and locate the outer thrust plate which holds the track frame in line. make sure the big nut on the end of the shaft is good and tight and you should have no problems.
Having said all this, if you look under the back of the machine and one of the castellated nuts which holds the sprocket shafts in is loose, get the correct gear to pull the shaft, (you need it any way to put the sprockets back on) and pull the shaft out until the inner nut is tight, then build everything back up. This is not such a big problem as it looks