Randy's ring and pinion has the parts you need
www.ringpinion.com or call 1 888 296 3129. you will also need a 3 series carrier for 3.07 gears, 3.73 are a 4 series carrier. I have good used and magnifluxed 3 and 4 series in stock if interested. In any case have the rearend shop check your axles for bearing and spline wear and install new bearings and seals in axles and pinion. Rearend shops here get in the ballpark 150.00 to 250.00 for the setup, a non posi rebuild with all new parts around 7-800.00, posi around a grand.