What part of the country do you live in? If it gets cold in the winters and heating bills add up, I would recommend stud walls rather than furring strips. Just because you can pack R-19 or R-21 in there. But I have seen a lot of articles using furring strip. (They often use the poly insulation boards between the strips) Will the furring strips leave enough room for electric boxes, though? Not the standard variety. But have you ever seen the ones mounted on the outside of the walls? The wire runs in channels and the boxes are mounted to the wall. I have never gone that route, but check out the options (at home depot for instance) and you can get an idea of what they look like. For standard wiring you would need a 2x4 wall. (You can use 2x3's even, but build the wall away from the blocks to give you the clearance.