Hey ssnider,
The reason for (most of) the discrepancy between the 2 reports are the speeds and altitudes at which the tests for the range were flown.
In the TAIC Report No.38 (the one I posted) the flight was at 168mphIAS/205mphTAS at 13,123 ft, using optimum weak mixture cruise for maximum range (with DT) of 2298 miles, for a flight time of 11.2 hrs under these conditions.
The ranges in the TAIC No.102D graph on pg.1 were flown with Normal power (the maximum sustained rich mixture setting) at an unspecified altitude. Obviously the power setting and rich mixture would increase the fuel usage a lot and decrease the range by a lot.
The maximum range (with DT) in the TAIC No.102D chart at the bottom of pg.2 was flown at 143mphIAS/146mphTAS at 1,500 ft for a range of 1844 miles, with a flight time of 12.6 hrs. 143mphIAS at 1,500 ft would be 175mphTAS at 13,123 ft. If we figure the ~same fuel usage per hour at 143mphIAS/175mphTAS 13,123 ft we get 175mphTAS x 12.6 hrs = 2205 miles for the range.
I figure that one or the other test was off a bit either in measurement, or assumed best economic settings. Or possibly the range value in Report No.38 was calculated with no allowance for climb to altitude.
Since this gives only 98 miles difference in range I think we can assume the numbers are fairly consistent?