I have never heard of HC Viva rack being the same as Escort,unlikely i would have thought as the outer tube mounts would have been specified by the car company if they outsourced to a supplier, but maybe the internals may be the same if they used the same supplier.
I would have thought HC Viva would be wider than an Escort ,but maybe its been modded.
I found this on the net where a guy is using parts from an escort and viva rack for his GT Viva HB,may not be of any help
https://www.annteak.com/update-of-wo...th-the-the-gt/
There is a HC Viva rack on the well known auction site at the moment,and does not seem to resemble an Escort one from the image posted on there.