Funny you say that, but it's actually a 401 GMC v-6. I always thought that the GMC v-6s valve covers from the 1960-1974 era resembled the 348-409 chevrolet v-8s, but when you view them side-by-side there's a BIG difference. One cool thing that I read about the GMC engine was that the spark plugs are accessible by the intake manifold instead of the exchaust manifold like a lot of v-type engines(less chance of burned hands during spark plug changes lol). From what I have seen, the GMC v-6s have a "GMC" stamped on the valve cover whereas the 348-409 has a chevrolet bowtie stamped on it(not sure about the truck engines). Here's a picture of a
409 and one of a
GMC v-6 Just my 2 cents.
