As far as I know, only one (1) Me 262A-1a/U4 was converted to carry the BK 5 (50 mm auto-loading cannon,) and that was (and is) the one pictured.
More here:
http://en.wikipedia.org/wiki/BK_5_cannon
In my opinion, installing 3 Mk-103 30 mm cannon in the nose would have been even more lethal.
The He 162 is having it's Lorenz 70 watt FuG 10ZY loop aerial looked at. Fitted on a teardrop shaped fairing, it was standard equipment on most fighter aircraft from late 1943 on.
Bronc