Not comparable, supply and demand. Go look for a 3.63 torsen, you won't find one for cheaper than the cost of parts + labor. (edit: you won't find one, hence the OP's question)


The supply of new 3.63 R&Ps is drying up and Bill Willner's price of $425 certainly reflects the lack of supply in the market. Not to mention you'd still be in for labor (assuming you can't assemble it yourself)

 

Here is a data point, based on my experience, for this discussion now that it has expanded a bit.

I started with a stock 7" Type-II Torsen with 4.30 gears (stock '99 differential)
I purchased new 3.63 gears (~$350)
A local experienced diff builder did the gear swap for $250
I sold the 4.30 gears, which were in great condition, for $200

My net cost was thus about $400. I am not including the value of the original unit, or my labor for installation and removal of the diff assy. The latter is not applicable here. The former is.

So I think the approximate value here is whatever a 4.30 Type-II Torsen diff assy (great condition) is worth, plus $400, plus the worth of the halfshafts. That should get you over $1000 easy IMO.

 

I just found an endless cache of 3.63 gears. You can PM me if you want and if I like you, or you can convince me to like you, I might tell you where they are.