a 4wd hilux diff will take just about anything you can throw at it..... they are used behind many 10sec rotors.....
for a CA they are probably an overkill... as they are heavy aswell.... and will definately need to be shortened....
you could get away with something smaller but since its not costing you anything to get you might aswell use it... at least you know you'll never need to touch it again.. no matter how hard you drive....
RC apparently the H145 has studs with nuts holding the centre in... and the H165 has bolts holding the centre in? can you comment on that since you have both?