stllookn,
I'm not sure when GM started using HEI. I think it was in the late 70's. To find out if you have a late model one remove the spark plug wire cap. Under the cap check for either points (round thingy) or a flat module that is kinda moon shape. If you have a module then its a late model HEI. What is the year model of your truck? Is it the original engine?
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Gerardo
1983 Custom Truck
TX Plates: "BAD BOW"
http://www.geocities.com/abetterchemist/