I think I have the Young-Holt; I have 'Mellow dreaming' and 'Born again' in a 2 disc set issued a few years ago by Water. If I have stuff, I tend not to notice further reissues of the material
As to the Castro, 'Groove funk soul' is a misleading title - though possibly it wasn't in the fifties But Teddy Edwards, one of my favourites, is always worth hearing in this context (well, or any context where he can play) - this is the same band that made 'Teddy's ready' for Contemporary.
MG
What MG said..........
It IS pretty straight-ahead but nothing wrong with that in my book. As well as the two albums he made with Teddy Edwards, mentioned above, the album he recorded at his home with Zoot Sims called "Live at Falcon's Lair" is also very good. Apart from these three albums and another he recorded for Atlantic with strings, I'm not aware of anything else he did. I guess partnering up with Doris Duke took away the need to have to work for a living. Anyone know whether he continued playing jazz later in life?
UPDATE:
I've just checked his entry on Wikipedia and see that he ended up playing in Las Vegas.