Seems like Vought have had the 'upgraded Vindicator' (V-167) flying, or at least a demonstrator. Main outward difference was replacing the TW Junior with a more powerful Twin Wasp, with 3-bladed prop replacing the 2-bladed unit.
Historical SBU-3 differed mostly from the earlier versions in having a much greater internal fuel tankage, 420-470 US gals (!!) vs. up to 168.
Question - how prudent would've been for USN/USMC to order such a plane some time in 1938? Export/Lend Lease worth? Addition of protection both for pilot and fuel should've been easier than on the SB2U with it's weak engine.
A good R-1830 of the era was supposed to make 1000-1100 HP, judging from what one can read here.
The speed would have been about the same as the Dauntless, and the range would have been greater (even with all SSFT and consequently reduced fuel). The folding wings would have been a benefit also (16' 0" folded vs the 41'11" of the Dauntless without fold).
The French seemed to feel the dive brakes fitted on their model were effective.
Hmm - I have not even consider the SBD not having the folding wing.
Relative thickness of the wing of the SB2U is surprising - 12% t-t-c at root, going by the data sheets (use Ctrl+F for faster navigation there).