If there are 4 valve releifs they are replacement pistons not factory, you can tell because they have chevy valve placement of the notches. I have torn apart hundreds of 318s and never seen one with 4 valve releifs in factory pistons. That is one big huge myth that needs to go away, just because most replacement pistons have them or even list them for certain years does not mean they came from the factory that way. I currently have 3 short blocks under the bench from 68 70 and 71 and none have valve releifs at all.

As you discovered the 714 is effectively the same as a 302, they ironically came on the 714 casting block also, they changed the casting number for the dakota because it used the bolts on the side of the block for the motor mount. And even stranger is with the changes made for a magnum 318 they also had a 714 casting number. 91 is the only one I have seen with both styles of oiling. The 92 and later magnums had a few early blocks with the hole drilled through the block but never through the head. It is always funny to me how much effort people put into blocking or plugging the passage in the block even though there is no where for the oil to go when the heads are on anyhow.

The 714 or 302 is only better than an X J 596... in a few aplications. They flow the lowest volume of air out of any SB mopar head EVER! Swirl and quench is nice but only trumps air flow up to a very low point in the spectrum of engine builds.