A lot of your questions can be answered by downloading the vehicle info packet on the GM Heritage website,
https://www.gmheritagecenter.com/gm-...tion-kits.html
You may have new questions after looking through the info packets- you may have to look at both the '67 and '68 packets as carry over info from the previous year may not be included in the subsequent year packets.
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'51 South Bend Model "9A"
'56 Chevy 3600 NAPCO
'74 Chevy Cheyenne Super K20-restored on 37's
'72 GMC Sierra Custom K2500- in progress
'08 GMC Envoy Denali
'12 GMC Sierra 2500HD Denali
'17 GMC Yukon XL
VCCA member #58596
http://www.nohrco.com