A while ago there was a lot of discussion on this topic, and nobody was able to come up with an easy, 100% effective solution. If I recall correctly, a Kyosho spur can be modified to fit on the stock center diff (forgot who did this, though).
SH Z-Car, Custom Crawler, 8s Savage, 12s XTM XLB 1/7 buggy, 4wd 4-link rear/IFS Pro4 truck, Custom Hyper 10 Short Course, Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz
A while ago there was a lot of discussion on this topic, and nobody was able to come up with an easy, 100% effective solution. If I recall correctly, a Kyosho spur can be modified to fit on the stock center diff (forgot who did this, though).
I tried it over a year ago when the .5 first released. Eventually scrapped the whole thing in my "do-over".