In my 2001 catalog I show a few different options for ported stage 6's.
P4876186- assy with 2.14/1.81 valves
P4876187- assy with 2.18/1.81 valves

They show 2 different CNC ported heads "machined for 2.18 intake and 1.81 exhaust" valves, but then the two different part numbers are listed as either:
P4876382- flat tappet cam(lifts up to .650)
P4876383- roller tappet cam(lifts over .600)
With a foot note stating that MW heads require offset pushrods.

If I had to guess....... I'd say the description of those two part numbers is incorrect.
I think they are bare heads and that one was std port and the other MW port.
(I realize these two numbers at one point were used for the Chapman heads, but I didn't think had arrived on the scene yet in 2001)

There is also number P4876991, which is listed as a service replacement assy for the 575hp crate motor.......90cc chamber.

And P5007484- "hi ratio assy, 78cc chamber"

Blofish, what part number is on the box for the heads you have?