I can not say, but our very own Pleat who hangs on this site probably would.
He should reply with the info for you if he`s not on Va ca with summer ending.
My Educated guess would be that judging by the era that its from and its 1-15 inch driver that its no more than 100 watts rms and in fact more like 75 watts rms of clean power!
It should work good for rehersal, recording and or light weight gigs, but if you play live with a hard hitting drummer and two guitars players you will likely want more clean head room!
Thanks. For some reason, I at first had the idea that the head was 150w, but further investigation seems to be pointing to around 70w.
I've seen the pictures of inside of one of these cabs, & it had a JBL D-140f 8 ohms.
This will be mostly for jamming & rehearsal, and I'm more into Amerciana-ish folk-rock, and also 60s garage rock (a la Louie Louie), so I don't need or want anything too super-loud.
(However, I will be jamming/rehearsing in a fairly large space (an old wooden church bldg), so I wonder will that fact require more power?)
Being new to this site I can't post links yet, but if you go to the Guitar Center website & put Kustom IIB in the search bar, you can see it.