Rear wheels (everything basically) should be installed.
Are we talking standard type wheelbase ? 5" WB ? Extended ? That relates directly to the typical COM which mathematically relates to the weight on the DFW. Everyone that measures COM has their own 'desired' or prefered value, but some people just have standard ways of weighting cars and manipulate a small amount of weight (< 0.5 oz) during track tuning without ever measuring COM.