Can I use a 400w hps socket on a 600w ballast not the bulb I can change those

OK so I have a 400whps and 600 w hps now can I change the light fixtures over only because the shade on my 400w is bigger I use that for veg but I really need a bigger shade and my 600watt shade can't be removed its riveted on and don't want to fuck with it so yeah my question is can I change them over cause the bulbs I believe will fit in each of them

yes

as above, yes