I just sold a srt diff with the 307 with wavetrac and tcu, I can get you a 307 with wave-trac for around 2600.00 + shipping.

the wave trac has never been in a car. (it's new),,, diff axle bearings ,,new.

I'll brake it down for you.
wave trac 1350.
axle bearings 150.
307 srt diff 800.
labor to build 500
total 2800
discount 200
as said above 2600.00 +shipping

if you need tcu for auto trans add 700.