The Ross holes replaced were his original 6th, 7th and 8th, plus a back nine par-3 (I think the original 13th).
The original 6th tee was about where the current 8th tee is and it was a mid-length par-4 following the first part of the 8th corridor.
The original 7th was a short dogleg left of 320 yards which was drivable, and it was famous for Ted Ray going for it four times in the 1920 US Open.
The original 8th was a long par-3 going back north, to a green site near the present 8th green.
The erasure of these three holes in 1979, with replacement by one hole (the Hinkle tree par-5 8th) opened up a lot more ground near the 18th hole for tournament logistical purposes.
The original par-3 13th (or was it the 12th?) was also near the clubhouse I think, and maybe it was erased for the same reasons.
Anyhow, all that left three holes to be accounted for, which were the three "outlying" Fazio holes added in 1979 (3, 5, 6 I think?). The original all-world 5th hole then became the 7th.