hard to find or rare parts?

[BurnoutNova]

what are some of the less common, rare, valuable, ect options and parts for these 73 and up style trucks? i have a couple 67-72's and am pretty farmiliar with those, but have been helping a friend work on his 86 K10 and just want to learn more about this generation truck.

i know tach dash's are hard to find, but what else is uncommon? did they ever put bucket seats in these years, in trucks anyway? he wants to put some 73 K/5 blazer seats and a console in his and i was just wondering if they were ever factory equipped.

thanks!