GSchnitzer, thanks; that would have been a nice inclusion.
nx1701g, thanks; I notice Memory Alpha has the same location for the pod as the remastered effects (which showed the gaping port from which the pod was jettisoned). Would be curious where they got that info.
The earliest reference--well, conjecture
--I can find that the ship's "ion pod" is way back on the engineering hull, back by the shuttlecraft hangar/hanger deck near the 1837 Frame Reference marker is in the book StarFleet Assembly Manual Number 3
by Paul M. Newitt. (This is copyright 1978.) This ion pod location coincides with a small little button/knob thing that's present on the eleven-foot Enterprise
model which has a little rapidly flashing strobe light.
Here are a couple of shots of some diagrams from the book:
It looks like for the Star Trek Remastered
project, the team decided to locate the ion pod where Mr. Newitt had located it back in '78.