[Jamie]

Thanks for all of the responses from everyone. I'll try to answer every question..

Jon, all of the caps have been replaced, including the filter caps. The hum is constant, regardless of volume.
Morzh, the speaker has three wires. I do not know which one is the anti-hum wire. I've not heard of that before.
Raleigh, I can try swapping the speaker wires. The wires had to be replaced when I restored the radio. I recall being very careful and marking each wire, but I suppose I could've made an error.

The resistor that's out of whack is #48. It's a 15k resistor that's drifted up to about 35K. I believe it's a 2 watt resistor and I don't have one in stock. If I bridge the 8mfd e-cap #67 with a 20mfd cap, the hum disappears. Could this be linked to the bad resistor?