All of these heads were given to me, and I'm thinking about porting and polishing which ever are the best ones. I know that none of these are high flow heads.

Have a pair of these.

346236 oval port heads. These heads have identical cast numbers, except one head has a large stamp that says GM4T and the other says GM2T. What's the difference, if any?

14092360 oval port. This one is brand new, still in the GM box.

Any info is appreciated.

236 castings are the peanut port heads (smallest intake runners). I believe (don't quote me) that the 360 castings are a mark 5 head.

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The 781's you have on the engine now are better in stock form. I would port those before I ported the peanut port heads.

Dave is right about the '781s vs. the peanut ports. However, if there is some reason why your 781s aren't usable at the moment (i.e. cracked)- Jakeshoe has done some extensive porting on peanut port heads and gotten at least one engine to put out 500hp using them. Do a search in Engine and HP topics for posts by Jakeshoe and peanut port heads and it should pop up somewhere.

Yea 346236 heads are the truck peanut port heads. They are great heads for a truck stump puller but I would leave it at that. I have a pair on my 454 in the Z right now. ok head it gets me going down the road. Im sure with work done to them they would make excellent power but not as much if you put equal work into 781s or something, But hey cant complain about free heads!