[fenbach]

i haven't needed external caps in my '36, like on the oil pressure sender, for example. i do use resistor plugs, however. i found that running a ground wire directly from the speaker to the radio chassis helped cut down on interference. if you're using an original power+speaker harness, make sure the braided shield is attached at both ends. and make sure the antenna wire shield is grounded at both ends. also that it's attached to the shields of the M and F plug terminals.
you can test the caps, of course, or just try replacing them [trial and error] with a modern 0.47 uf cap. there's nothing special that i know of about the original ones in metal cans. and the old ones likely do leak.
hope that helps.
bob