[BR3W CITY]

I've read the whole thing, or at least as much of it as pertains to me as possible.
There is no mention of the word "external" or "Exo" pretty much anywhere in mentioning cage and roll bar requirements.

The "open top" and "sandrail" rules also don't mention anything specific to that (and since those would be the only other applications of an external cage, aside from a rockcrawler) I guess it should be ok.

To clarify; are supposed to interpret the NHRA rulebook the way Thomas Jefferson viewed the Rule of Law...that we CAN do something, unless it specifically says we CAN'T?