1968 Dart Slant block differences

[SCOTT EVIL]

Hi, new here, very nice site. I have 3 1968 Darts, all slant 6 with automatic. One is a 170, and two are 225. I just noticed that one of the 225's has the driver side freeze plugs in line with the rib off the back of the water pump.
My other 225 has the freeze plugs up higher, kind of under the exhaust manifold. And the part number cast in the block is different between the two.
Why is this different?
Thanks, Glen ( a fan of Dr Evils son, Scott Evil )

 

[MadScientistMat]

1968 was a changeover year - they went from a 3 freeze plug block to a 5 freeze plug design on the 225. If one of yours is a 3 plug version, it may be a leftover '67 block.