What would YOU do?

Those heads plural, meaning any of them. X,J,O, or Us.

-FYI. The ethanol fuels are NOT crap, well mostly not anyway. They are actually more resistant to detonation. And once you get the tune into them they do very well for our streetrods.They just dont keep their volatility long in open storage, such as your carbed fuel system.
Its hard to get a sense of your mood, personality or ego from just the few posts you have made.And the following is not meant to be in any way hurtful.
-Getting back to the heads and the now stated "streetrod" usage.I cant think of a tactful way to say this, but I will try;It seems to me that your budget is quite small, or you are stuck in the "oldschool" way of building.
-If your budget is quite small then you may have to make do with what you have.
-If, on the other hand, you are building oldschool ways, then there will be no changing your mind, and you will reject any, and perhaps all, advices offered.Every single person who responded to your post, has given good advice. But you came back with hell this and crap that.But to your credit, you asked which heads and why.
-So, if you truly want to use one of those iron open chambered heads, in a streetrod,and even though I doubt it makes a whole lot of difference which ones you use, I would answer; the Js, and the why is because you already have them, and they sound fresh.
-On the off chance that Im wrong, and that you might be open to change,you could ask/say something like; Hey guys, Id like to build a fun 340 for my A-body streetrod.I will be using a 4 speed and either 3.55s or 3.91s.It will be used mostly on the street with little/no highway cruising and only occasional trips to the track, just to see what she will do.These are the parts I already have: -( then list what you got). What changes might you suggest and how do you suggest I assemble it to run and survive on todays oxygenated fuel.Then tell us what fuel you would like to run or be willing to run, and a budget to fit it all into.And the final qualifier would be something like;I would like it to pull like a freight-train, in 2nd gear from 35MPH.
If you do this, you will get some of the most knowledgeable fellows in all of Mopardom to help you reach your goal(s).
-Hope this helps