Okay, jtb has solved the immediate problem by mailing me a tube to replace the one that's torn. Still, when I was at the auto body shop with my car today I thought "self, you're in the right part of town where all the car and bike shops are. let's take a look around while they're working on the Subaru".
WILD GOOSE CHASE.
I have been to at least 1/2 dozen auto parts stores, 3 or 4 foreign auto repair shops, every bike shop, two custom bike builders, and the chain saw, etc. place (he had funky pink 5.5mm). Not one place has the 4.5mm or 5.5mm line. Oddly, two places had SMALLER lines; for old VWs they told me. I'm just sort of amazed...
So, thanks to jtb I can use the carbs as is, but I still think this fine old bike deserves fresh lines. I'll just keep my eyes open when I'm in ABQ, or talking to suppliers/dealers about other parts.
Pretty strange.