I'm not sure what you mean by the grill dimension. The woofer cutout is 5 5/8" and the full diameter is 6 5/8". They're 3" deep. The tweeter cutout is 2 1/4" and the trim ring is 2 5/8".
They don't come with woofer grills. What size you want would depend on how it's mounted. If you want to try to find a grill that has mounting holes that line up with the speaker mounting holes, they're 6 1/8" center to center.
If you flush mount the woofer in the pod (you need the 5 5/8" hole with a 1" ring around it set in 3/8" deeper than the face of the pod) then any grill bigger than 5 5/8" will clear the surround and you'll just need grill clamps that screw in outside the speaker diameter.
Sounddomain's shopping site says that they do. I will call ID tommorrow to find out for sure.
I kinda want to mount them in the pods so that the top of the grill only sticks out past the surface for the pod only a little bit. At least thats what I THINK i wanna do.
It probably would be easier to just face mount them.
I have the components, so maybe the separate mid basses come with grills? ID has their own forum at the SD forums where a tech can give you an answer about it.