[Texasrocker]

Hello David B, Welcome! I took a quick look at the JF Riders schematic for the Philco mod 42-380 parts list.
It shows that the set originally had 2 electrolytic condensers mounted in one unit. IE: 2 separate leads from 1 electrolytic can chassis-mount type
condenser. Negative polarity of orig electrolytics is most probably the orig tubular can (if still mounted to chassis, to chassis ground itself?). If someone replaced the electrolytics before under chassis, you will probably see 2 separate larger-size old cardboard type tubular replacements with a ( +) end on them both.
The JF Riders schematic shows both orig Philco electrolytic condensers for your set were the same value in ufs, and same voltage rating. IE: 2 electrolytic condensers rated at 8uf @ 475 volts.
Good modern day subs would be: (2) individual 10ufs@500 volts electrolytics types replacement condensers. Closely observe polarity +/- on the old caps installed, and if both (-) ends go to chassis ground, sub in the new (+) ends from each electrolytic to their respective solder locations (+) ends of the old electrolytics caps installed now, twist together both the negative leads, (follow printed arrows) for neg ends of both new caps, and solder them to chassis. Remove the old electrolytic caps one at a time by subbing-in the new ones. Unless your chassis has a "floating isolated ground for the new caps (-) side, you should be "hum-free", and safe to bring the set back to life. Check a schematic first for free at: http://www.nostalgiaair.org .
Good luck restoring your Philco!!