The "Figure 8" is supposed to mean the 440 block is for a motorhome application, which means "high flow" system. BUT, in reality, the cyl head gaskets were all the same, which means that only one part of the Figure 8 passage is open on the head gasket, so no advantage over a normal hole there, as to flow. BUT on the engine assy line, it "meant something" to them, which is important.
The implication is that the larger hole will flow more coolant and all of that . . . until you realize it's not that hole, but the size of the hole in the head gasket that controls the amount of coolant passing through to the cyl head, instead.
When I read of that "hole" in the old Mopar Perf Race Manual, it was mentioned for a 440 motorhome block. Not surprising that some also made it into 383 blocks. The 440 motorhome engines had unique cyl heads from any other B/RB motor, but on the ONE set of them I saw in person, I didn't think to look at the head deck surface for a matching Figure 8 hole.
Do you know the particular applicaitons for the 383s you have?
Take care,
CBODY67
