Reference 3US P-47D-26, V2.82.100
Francis H Dean reference:
Speeds are TAS
The USAAF data show 340 mph max Military power at 2,500 ft.
Narrative states that early P-47's had SL speed of 325 - 335 mph for early models.

My tests show that engine Power_scalar = 1.14 will give those numbers at 50 pct fuel.

The 26 had the bubble canopy, paddle blade prop and water methanol injection.  Some 250 lbs heavier than prior 47's, the prop did not increase speed but significantly increased climb performance.  In fact, the 38 and 47 were good climbers; the 51 not.