I think you're right Antag, I don't think even his current signature pickups are all that high in output, let alone his old ones. I'm sure he used P90s sometimes in the early days as well.
He almost used single coils, but his Strat broke just when they started recording the first album so he used the SG. Just think, if that Strat hadn't broken we'd be here right now trying to decide what was the best Metal pickup, the Apache or the Mothers Milk :lol: