Spools will damage the shafts very quickly, i snapped a pin on the cvd's within 10minutes in snow.
The spools for the old diffs are quite hard to find, the new ones won't fit.
any maxx diff will fit with a slight easy mod to the shafts, as they are shorter than the old diff.
as above ebay is maybe best option with all the chop shops selling them new.
I got a new revo spec Tmaxx diff bought new diff carrier and I-bar now it's a brushless diff total cost about $15 but prices have gone up slightly since i done it.