Galpin Ford in the north San Fernando Valley of SoCal, currently has 316 2013 F-150's in stock....they sell many each week, and many new ones are rolling in each week.
Just from my looking at their stock over the past couple of weekends, I would say that the low-end trucks (fewer in number and many are the white work types) are mostly the 3.7's; and the mid to higher-end trucks--XLT, Lariet, FX4, Plat, etc. are all predominantly 3.5 EB's--and significantly more than those with, the 5.0. Just a swag...I would say, well over half their trucks in stock right now, are EB's.
This is a very popular engine here; since the first of the year, virtually every new F-150 I have seen on the road in L.A., Orange, and Riverside Counties, have the EB logo strip.
FYI: Gas has been well over $4.00 a gallon for many weeks now, here in SoCal; although, it has moderated to some extent ($4.11) over the past week.