There were a few different pick-ups used in those solid-body Gretschs from Cincinnati of the mid-70s.
There was a guy in a C&W band from San Bernardino who thought his Super Axe stock pick-ups were WIMPY, so he wanted ones that would scream when playing lead licks ! ! !
I'd contacted Duke Kramer to inquire as to if there was a pick-up supersession that matched the instrument's electronics, but by that time the Super Axe had already been discontinued and the parts inventory had been completely exhausted. He'd suggested a DeArmond Humbucking as the mounting was very similar, but they just didn't have the output the guy wanted.
I'd installed a pair of Ibanez Super 70 Humbuckers, which at that time were THE HOTTEST PICK-UPS around -PERIOD ! ! !
BTW . . . From what I've been told by Ibanez guys is that Maxon & Ibanez pick-ups are made in the same factory of a manufacturer who produces pick-ups for several guitar brands to their individual specifications.
Here's a link sent me by an Ibanez collector, whom I'd sold him his first back in '76 when they retailed for $300.00 w/case . . .
http://en.wikipedia.org/wiki/Maxon_Effects_PedalsAccording to Wikipedia my pick-ups were manufactured 28 Oct. 1976.
Here's photos of my LAST pair that I've had since the mid 70s that are going up for sale soon . . .


They were so hot, that he brought the instrument back to have me install a DIRECT BY-PASS SWITCH, so he could play rhythm chords around the on-board electronics with ZERO parasitic signal loss . . .
That was a real PITA, (and NOT the bread either) as I had to custom stack contacts & insulators from three 90 degree Switchcraft toggles to make one switch. I think I might still have the hand-drawn schematic kickin' around somewhere . . .