Awning rail diameter?

[Kristijotex]

First, I've been lurking about this forum forever. I can't thank all of you enough for sharing all of your wisdom!
I've FINALLY got my *first* Airstream. I can see already that this is a bug that bites hard. I know that there will be others in my future.
I've got a '64 Trade Wind. It's mostly original, with all of the joy and pain that goes along with that. Previous owners replaced the fridge and installed a tankless water heater. Thank goodness the hubby can repair plumbing! We'll be tackling the gas lines this week. PO's never even tried to light the stove! Should be interesting.
Now here's my question of the day. Were the ORIGINAL awning rails on the '64 Trail Wind 3/8"? I know that 3/8" was standard on lots of the older vintage campers. That is what I've got on my Serro Scotty.
I'm making a rope & pole awning (not my first rodeo) and I'm planning to use PVC wrapped airplane cable to make the welting. Just want to make sure that I buy the correct sized cable.
Again, I thank you so much for sharing your knowledge!