on the front driveshaft...tom woods is a better option.
tom woods now has a new flange that he is having made that is about 3x as strong as the spicer unit.
I blew up a spicer unit about a month back and Tom Woods set me up with his new style double cardan driven flange. instead of being made from cast nodular iron it is made from a forged steel...looks pretty similar but is way way stronger.
this being a cross-over jeep part they use in the 1310 series rover front shafts even though there is not alot of talk of failures in the rover world they had seen plenty in the big tired jeep world so Tom went out and improved on the culprit part to eliminate the weak link.
http://www.4xshaft.com/index.html
when mine failed they turned mine around same day to have me wheeling again...its very hard to expect better cutomer service then that!!!