What fitting is typically used for the vacuum port on the rear of the manifold on the 383?
Do you have power brakes ?
I have one.PM me your phone number and I will shoot you a picture.
They are sold on eBay.
It will depend on the options ,
Power brakes is a single fitting , add ac & there is a small second line to actuate the doors , add cruise control & you may have a second smaller nipple for a 3rd line .
Thank you. I just ordered this one.
https://www.megapartsusa.com/proddetail.php?prod=101-154