Here's what I have. A V6 LWB front diff housing, LSD from a Starion going into an 88 SWB. Everything lines up great except for the drive side (left)axle shaft. This is not a spline issue it's a diameter issue. The 4cyl axle is smaller so this needs to be upgraded. When I assembed this the first time I thought the axle was engaged but a quick shift in to 4w and I realized something was wrong. I put the question up a few months ago regarding the axle and there wasn't a positive consensus to which axle I needed.
So keep this in mind, and of course be prepared to pop some ball joints to get the axle shaft out.

Sorry, I missed your past post. The answer would have gone like this:

1) 88-89 Quest LSD fits into V6 front housing and needs the V6 half-shafts for the SWB. Really only the DS is needed if you use the V6 center tube. But why not match them as the V6 is a larger diameter.
2) 87 Quest LSD (maybe 86?) fits the V6 housing and retains the 4-cyl half-shafts.
3) Older Quest LSD (pre-87?) fits the 4-cyl housing and half-shafts, with additional shimming.

McV's correct- If you're axle seems too small, then you have either an 88or 89 LSD. Just swap in the V6 axles and you'll be set. The knuckle end is the same, so nothing else has to be changed.

I think Chris was posting that he ahas figured it out now, and was giving a heads up for others.

Exactly, for one reason or another this was not clear to me.
I do know the LSD is an 89.