wow what a post - I am glad to look @ 79 corolla interior. My dad bought a 76 back in 76 and we had until 88.
Well about the difference in interiors - I think I remember what changed from 76 to 77 and then in 79.
76 used to have round dials and speeds in mph only. Rest of stuff in 76 and 77 was same - though front grill was different. Corolla 76 had a vertical lined grill - and 77 had a hohorizontal lined (tightly knil) front grill.
From 77 onwards speed was in kmph (I suspect these square dials came in 78/79 and not 77 but not sure) - but speeds were measured in kph from 77 onwards that I am certain of. And both 76 and 77 didn't have this 3 spoke steering wheel - It came in 76/79 with a few body trim differences, front grill, front and back lamps. 79 used to look bigger to because of larger bumpers.