The Keystone XB-1B was the designation assigned to the Huff-Daland XB-1 after the original Packard 2A-1530 engines were replaced with Curtiss V-1570-5 Conqueror engines (Huff-Daland was reorganized and renamed Keystone in 1927 -- between the time the XB-1 was built and the XB-1B was modified). The XB-1A designation was skipped because it was already assigned to the Dayton-Wright XB-1A "Bristol Fighter."
The improved B aircraft had better performance than the original, but still didn't compare favorably to other aircraft of the period and never entered production. The performance of the Curtiss XB-2; for example, was significantly better than the XB-1B, but the Curtiss aircraft was initially rejected also; in part because it was too big to fit into existing hangars.
XB-1 with new engines
TECHNICAL NOTES: Armament: Six .30-cal. machine guns and 2,500 lbs. of bombs (up to 4,000 lbs. for short distances) Engines: Two Curtiss V-1570-5 Conqueror V-12s of 600 hp each Top speed: 117 mph at sea level Service ceiling: 15,000 ft. Range: 700 miles with normal full bomb load of 2,500 lbs. Span: 85 ft. 0 in. Length: 62 ft. 0 in. Height: 19 ft. 3 in. Weight: 16,500 lbs. gross Crew: Five Serial number: 27-334