I've got a Philco 42-390 cabinet that I ended up putting a 42-380 chassis in. I actually ordered a printed copy of the schematic (42-390 chassis) but the 390 chassis was too far gone and I got a 380 chassis of ebay, recapped and installed it (now working).
I went between the printed 390 schematic, the illegible 380 schematic, and reading the values of the capacitors in the chassis when I did the recap. It was a bit of a bear but I got through it in one sitting. A really hot soldering iron, mini diagonals, mini needlenoses, a desoldering bulb, dental tools, precision screwdrivers, and heatshrink tubing are your friends here
Also the rubber insulation on the wires in this radio are disintegrating. I replaced a bunch in mine, and did heatshrink tubing on the ones I couldn't replace.
As far as 6X5 rectifiers, I threw out the box plate one that came in mine and used a heavy duty JAN 6X5GT, which has X shaped plates like a 5Y4 and is much less prone to shorting out and smoking your tranny.
EDIT:
The three pin connector on the back is for an external antenna for the shortwave/police band, not for a phono. you'll have to tie to the volume pot wiper and rig a switch for a phono input. (I modded mine for a Pilot FM tuner which has a built in input switch)