Ring and pinion inst. kit

I´ll replace the 2.76 gear in the rear with a 3.73 gear, (see second link)
any of you guys got any experience of this ring and pinion kit?
Also considering the installation kit from Ratech (see first link), would this be worth the money?
The center chunk was rebuillt when I had the car apart, have had it running apprx. 50 miles since then. Would it be enough with replacing the crush sleeve and gaskets in the center section?

http://www.summitracing.com/search/?keyword=ratech 301k&dds=1
http://www.summitracing.com/search/?keyword=motive gear c887373e&dds=1

Many thanks in advance
Lenny aka Swedefish