[James]

I tried to look up some information for you, not much out there. I did find some links that you will find helpful:

Facebook group for the 702 V12
https://www.facebook.com/groups/2199192940390615/

Possible manual
https://www.autopaper.com/gmc/b7000.php

Owner's and Driver's Manual
https://www.abebooks.com/servlet/Boo...?bi=9579867786

ThunderV12, LLC
https://thunderv12.com/

the 6066 GMC Guy web pages
https://6066gmcguy.com/

Misc. video and information
https://www.youtube.com/watch?v=ni4eX-DZAAA
https://www.macsmotorcitygarage.com/...ubic-inch-v12/

Have fun. Great project. Some of the other members might have more info for you.