Low Back Bucket Seats

[IllinoisK30]

I just acquired a 1977 Chevy K30 SRW standard cab from Arizona a few months ago. I am super excited to finally find this and very eager to start working on it.
My question is weather or not it came with low backs or high backs? This is the first truck I have dealt with bucket seats. I am aware that this was a transition year to the high backs. There are some rub marks on the back of the cab below the window from the original seats. I suppose either high or low back seat could have made them.
Does anybody know when they transitioned from low to high? I know that’s asking a lot but I have faith in you guys/gals. I’ll post some pictures of what I know on the truck. The documents in the truck say it was delivered on 4/77. Would that be early enough to have the low backs.
Thanks for any and all help with this. I want to restore this as correctly as possible. I do have a want ad in classifieds for the low backs.
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