The width for these things seems to be consistantly 11' 6" in all the sources I've checked but the lengths vary. There are the usual problems with "length" given as overall ( including gun overhang ) length but the sources I do find that give the hull length in the range of 6.33m - 6.51m ( 20.76 ft - 21.36 ft ) with another source giving the hull length of 21' 2"
This website
http://afvdb.50megs.com/usa/m26pershing.html breaks things down even further giving a "Length without gun, with sandshields and pintle" of 249.1" ( 632.7cm ) = 20.76 ft. and "Width over sandshields" of 138.3" (351.3cm) = 11.525 ft.
The two line drawings I have when checked as a ratio of width to length is 1.8. Given that we know the width all sources seem to agree on is given to be 11'6" ( 23 pixels ) that would make the hull length for an Icon at this scale to be 42 pixels ( 21 ft ) so the original Icon at 22x39 pixels isn't really any further "off", dimension wise, than the new one at 46 x 24. The new one is prettier though
Don