I have a 73 elcamino and a 78 catalina sitting out frount, which would be the better car to take the disk brake setup off of? The camino looks in better shape but im not shure which would be easier.

Charlie,

Both of these would be considered 'Tall Spindles'. And so if you wanted to used them on your '72 you would have to do the 'tall spindle' swap. (Just wanted to be sure that you were aware of that)

Ok, now the differences between the two as far as I know:
'73 camino should be 11" rotors and small (.750") outer wheel bearing.
'78 cat should be 12" rotors and should be the large (.850") outer wheel bearing.

Both will work fine, but if you are willing to take the time to get a few measurements, you might have a better brake package with the '78 Cat spindles.

Good Luck