I would contend that no Iran was not a "Top" priority, but was one of several nations not just in the ME but around the world that were given favored status in foreign military sales for geo-political reasons. Iran had much to recommend itself as an ally, between its position of the frontiers of the USSR, petroleum reserves, and compliant government the kingdom was poised to leverage plenty of aid and approval of sales from the US.

But they weren't the only one at the time getting the best of the best even compared to peer states. Lets just look at the most famous example in the F-14. It was not just bought because it was new, but to fill a specific need, that being to be a credible threat to the new, fast and high flying interception MiG-25. For that to happen there were basically 2 options from the US, those being the F-14 or the F-15, and in bidding and demonstrations Grumman struck the better deal and got the bids.

However the F-15 was not without export orders sought and approved at the same time. Israel was the first foreign buyer to get the Eagle and began to receive them in 1977, while Japan and the Saudis would get their own soon after(it should be noted though that the Saudi sale only occurred after the Iranian revolution). So at the time of the fall of the Shah both of the US's premier interceptor aircraft were in operation with allies in the region. While heavily upgraded F-4's still rolled off the factory floor and to virtually every nation allied with the US around the world including Iran, Iraq, Egypt, Turkey, and Israel.