Unusual Chevy 348/409 -truck engine?

Here is a pic I grabbed at a boneyard the other day. Sorry I wasn't more thoughtful in the composition. The engine is sitting in a Chevy pick up. It differs from most 348 engines I have ever seen. One, the oil fill is in the valve cover, rather than through the intake manifold. The intake on this engine is a two barrel, I have never seen that on a 348. Also, the intake manifold is "raised" with a valley pan under it. I don't recall ever seeing a similar set up on a 348/409. All the ones I recall have the manifold sitting right in the "valley". Does anyone recognize this set up? Is it some type of truck atrrangement? Also, what seems like an oversize water pump housing and a double belt alternator/genrerator.

This isn't a 348/409, and it isn't a Chevy. This is a GMC 305 V6. They were fairly common through the 60s in all sorts of GMCs from pickups up to 60-series trucks.