Overall I think NASA made the right choice selecting the Grumman design, but it also got changed a lot during development. Who knows what this one would have become if it had been selected. The use of the same engines for descent and ascent is an interesting way to save weight, but those extra medium-sized (backup?) engines might have used up much of the savings.
The description of the images in the original Flick gallery calls them "standby thrust chambers":
Convair's proposed vehicle featured a single throttleable main engine backed by two standby thrust chambers. It was to be a partially staged configuration with a side-by-side crew arrangement and a probe-drogue docking mechanism. The lower structure held the descent tankage, which was to be depressurized 15 seconds prior to touchdown. The depressurized tankage, along with the crushable vehicle skirt, were to offer a back-up to the landing system in the event of a landing accident.
The engines were protected against landing damage through use of a crushable main engine nozzle skirt and the placement of the standby engines above the descent tankage.
The Russian LK also used a single engine, without any backups.
What I don't see is a hatch for egress on the surface.
Was the plan to go out through the top and down a rope ladder? Or not to do EVAs at all? Or maybe they hadn't worked out that detail yet...
I was wondering the same thing. It seems that there's a side hatch:
http://www.flickr.com/photos/22948295@N02/2217192111/ (the line drawing shows an oval hatch over the RCS arm)
http://www.flickr.com/photos/sdasmarchives/7142967369/ (inside view towards the back of the cockpit, shows the open hatch)
http://www.flickr.com/photos/sdasmarchives/7142968041/ ("Angry Bird" side view, I think that the closed hatch is barely visible, as it's white-on-white)
Given the position of the hatch, I guess it would require a rope or a ladder on the nearest "back" leg.