CV Joints

I seem to remember reading that early and late cv joints are not interchangeable as they have different spline numbers. Is this correct? Would early front shafts and cv joints as an assembly - 2000 - fit a late -2007 - car? I know the diff end is the same number of splines - 22 - and I presume the outer flange end is the same as there appear to be only one type of freewheeling hub offered across the range.
The reason I want to know is that I have a pair of shafts and cv joints from an early car which I would like to use as spares on a late car if/when I brake a cv joint.
As an aside has any one used D&Gs Birfield rings on their cvs and do they really make a big difference?

ive had 3 CV's go on mine, but have all failed differently, one the outer gave up, so like you say the rings would help to beef up the CV, but then something else would be more likely to fail, when at the big jimny event it seems the inner part with the splines gave up on me

ive been speaking to a transmission manufacturer today as he makes uprated CV's halfshfts etc, and from his experience its the cage that hold the balls fails quite often and then causes the CV to go

he was quite surprised to see how thin the cage was on jimny CV's but he's comparing them to Subaru CV's

we looked at the possibility of using a larger CV's and making custom halfshafts to suit but there just isnt the room in the jimny axle to do this

the only other method is making the CV's out of a stronger material but thats when the cost goes up!!

no thats the thing just an open diff, its probally when the spining wheel does get that bit of grip

at big events now i might just take a set of front halfshfts with me as i can change them now within the hour

Thanks guys for all your info - there's nothing like experience to give a good response! My auto Jimny is not actually the car I am thinking of as I have bought another one to replace my French Sammi. Its the one that Jamie on this forum had, and I'm taking it to France and will register it there. Its a manual so perhaps a bit harder on the transmission. The events that we do in France involve a lot of rocky tracks and rocky steps etc. so quite a strain on the transmission. I have now taken the lockers out of the auto and put them in this one.
I'll have a look at Kam - hadn't thought about them but a good idea. Do you know if their shafts are the same dimensions as standard? D& G are certainly expensive but I guess good quality - the other possibility too is ERM in France who sell uprated shafts and cv joints although with the joints they are exchange which makes me think they put something like a Birfield ring on them, but the shafts are cheaper than D&G!
The other quandry I have is the tyres - I have a set of 30.950.15 Kumhos or a set of 235.75.15 Insa Turbo Special Tracks. The Special Tracks are more grippy but also put a lot more strain on the transmission! As it has lockers maybe the Kumhos will be better in terms of breakages as less grip but with the lockers unlikely to spin/grip/spin as much. Decisions!!