Jack,

Take a picture of the truck data plate and post it here. According to this GMC site page for serial number plate locations, you will find the data plate "Located under hood on R.H. side under cowl."

Many folks will chime in to help figure out what it is if you can provide that. thumbs_up

Dan

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)