There were some developments going on in those seven years between the respective debuts of Vanilla Fudge and Rush that probably should be mentioned with regard to the roots of heavy prog; Uriah Heep, certainly. They were doing fantasy lyrics before Rush, and plunged deeper into fantasy themes than Led Zeppelin did.
There were also a number of prog bands that weren't really metal but had one or two really heavy songs in their catalogue - King Crimson and "21st Century Schizoid Man" was influential, Genesis and "The Knife", Atomic Rooster as well. Deep Purple's earliest albums were very Vanilla Fudge-like, and of course there was that whole "Concerto" experiment. This was still in the days when Black Sabbath and Yes toured together; metal had yet to be really defined as a movement back then and there just wasn't a lot of it around yet, so I would say that "pure" prog bands were still strongly influencing the course that prog metal would take.
And if you only know Journey from the '80s with Steve Perry and "Don't Stop Believin", you might be surprised to learn that they were actually a prog band with some fairly heavy material when they started recording around the same time as Rush in the '70s - try listening to their 1977 instrumental song "Nickel and Dime" back-to-back with Rush's "Tom Sawyer" sometime.