The A20 was a smaller aircraft with a hard nose and 6 50cal's. It had 1600 HP radials and was used as a fast attack strike bomber with a secondary capability as a night fighter. The night fighter part wasn't used because the P-61 came along. The A26 was similar in design to the B26 but in reality it was very very differernt. The A26 was designed from the ground up to be an interdictor. The most fearsome combination of firepower available to allies from the late 1930's upto when the F-14 tomcat came into service, nothing could haul as much ordinance as the A26. Available in several configurations, some mounting 20mm cannon and a 50cal combination in a hard nose, to having 8 50cal's in the nose followed by 3 50cal's in each wing, and mounting rockets + an internal bombload. The A26 would accellerate rapidly to 400mph according to Dukemskt. Dukemskt, who is a member here and also happens to be my boss was an A26 driver during Vietnam and the following to say about it.
"One night we came upon an old GMC duce and a half and strafed the ***** out of it. We came back around and it looked like a *****ed up GMC duce and a half, so we rocketed it and napalmed it. After that it was a *****ed up burning GMC duce and a half and is probally still on fire today."
Interesting note about the A26, it had a roll rate that was phenominal - even greater then that of the P38 or P61. It would roll so fast that if you were not careful you could red out. It was a fantastic plane that was overbuilt, and as such still see's service as a borate bomber up in the northern canada territory through Airspray services.
Best,
Wolfala.
P.S. I have the pilot operating handbook from 1945 that I scanned into PDF format if you want it. Same goes for the P51D/K, P38L and P47N