Well, if it is "Original" and only rebuilt, it will probably be a 228 or a 248.Someone may have upgraded to a 270.
Is it an original GMC engine?If you look at the distributor,just to the left there is a machined pad on the block at the base of the distributor. The first three numbers will show something like 228 or 248 or 270. cool

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
-
-
Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!