Both the JDM 1st and 2nd GEN b16's were stamped with the "B16A" on the block. However the 1st GEN b16's used cable trannies (S1/A1/J1/YS1) while the 2nd GEN b16's used hydrolic transmissions (SC4/Y21/S80/Y80). As far as specs go, the 1st gen b16a's were 10.2:1 motors in (90-91 Civic SiR/SiR II, 90-91 CRX SiR/SiR II, 90-93 Integra XSi) that made 160 hp @ 7600 111 lb-ft @ 7000 while the 2nd GEN motors were a 10.4:1 motor in (92-95 Civic SiR/SiR II, 92-96 CRX SiR/SiR II, 96+ Civic Vti, and 96+ Civic SiR/SiR II) that made 170 hp @ 7800 116 lb-ft @ 7300. The overall outside appearance is basically the same between the two motors, though the Intake Manifolds have a few less vacumm lines running off the IM than the USDM spec motors. My brother has a JDM B16A in his 94 civic coupe so I'll look at the head and intake manifold numbers on them and post them up for you... I think the head should be marked with "PR3-1" on the right frontal side of the head above the exhaust manifold.

As for the USDM motors, they've only made two different models which are the B16A2 that are found in the 99-00 Civic Si Coupes and the B16A3 that are in the 94-97 Del Sol VTEC's both motors were 10.2:1 CR and made 160 hp @ 7600 111 lb-ft @ 7000.

Hope this helps, if you need more specific information just let me know... I'll check out my brothers maybe tonight if I see him so I can post up all the numbers for ya.