Th two pairs of jets were an add-on for the B36. This was so that it would achieve a certain speed and alltitude over the target. Six recips were more than enough to get it airborne and in the cruise it was common to shut down a couple of engines. The jet pods came straight off the B47 and had iris shutters to block off the intakes when not being used.
That's what a USAF major told me in the early 60s walking round the one they had at Offut.
It was fully serviceable and had a war target. One of the conditions General Le May had set for it's preservation.
"There are no free lunches in SAC."