[Arran]

You could, possibly, but if this is one of the sets that I am thinking of it likely isn't practical. A 78 rpm machine, regardless of what you do with it, would be very hard on LP records, they weren't designed for dynagroove or stereo records so the tone arm weight alone might damage them. The easiest thing to do would be to find a separate 33 rpm record player and pipe it into the radio either through wires or a wireless transmitter, that way the original unit stays intact. I don't think that a Garrard, BSR, VM, or any of the later changers would fit without substantially modifying the cabinet as the original machine was specifically built for Philco.
Best Regards
Arran