Porsche would say 50/50 since they're the ones who balanced the use of aluminum, transaxles, battery location, and pulled the motor back until things were all balanced perfectly.
Road and Track reported in 1983 that it was 51/49. Big deal, not sure a fillup of gas would make much difference really.
Check out the specs on this article I posted on the 944 Pelican site, it's the road test between the Vette, Ferrari, 944, and 928. It shows the R&T version of the weight balance issue, etc. Not sure about the accuracy.
http://forums.pelicanparts.com/showthread.php?threadid=259247
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