You'd have to pop it open but I'd assume 3 Mars drivers in it at around 50-100v and ~.7A.
Couple of these per driver is probably the best bang for your buck for mars conversions.
http://www.cutter.com.au/proddetail.php?prod=cut2827
Or a pair of cxa/b3070 3500k 80cri generally for your all purpose spectrum. A single 72v cxa/b3590 can be ran on them, or 2 36v for higher efficiency. But if you want to push the higher efficiencies, not much point in leaving them on Mars drivers(they're 86% efficient iirc)
Footprint is limited by beam angle and height above canopy. Beam of unreflected Cree cobs is 115°, so a 12" hanging height means at 19" from the center light is about half the amount of light the center receives. This can be calculated.
Side a being the height above canopy, angle beta being 1/2 the beam angle(57.5° for bare cobs, 45° in 90° reflectors) and side b being the distance from source where 1/2 the light would be.
http://www.mathportal.org/calculators/plane-geometry-calculators/right-triangle-calculator.php
Samsung strips might be a nice way to get a little more oomph outta the driver(if 100v drivers, and if they'd fit in the case) they're ~24v per at .7A drive current.(I believe there right at 160lm/watt at this current)
https://www.verical.com/pd/samsung-misc-products-sib8t341560ww-904038