Those vac lines do tend to get old and brittle. I don't know if Ford still has them (doubt it) and don't know of any aftermarket companies that offer a replacement. With that said, I had to replace mine and tried 2 different methods.
First, I went to a local auto store and bought some hard plastic vac line hose. It's easy to find, NAPA, Auto zone, Pep Boys, and you need to buy some rubber vac line adapter plugs while you are there. I went through several sizes before I got good rubber adapters that fit both the vac line and valve nipples. Just ran my own lines and followed the original routing.
The second time I did this I bought some different sizes of rubber hose from the auto store and just ran rubber hose direct from nipple to nipple. Easy and cheap! Just keep the rubber hose away from the hot exhaust and it works well.
Hope this helps.
Ken