The B-29 and B-29A were visually indistinguishable but were separate. There was a 1 foot wingspan difference between the two based on the wing center section construction but was sufficient to warrant a new designation. The B-29A was a B-29 built in Renton (BN). As a penalty for the new (and better) wing construction technique on the 29A, the useable fuel was reduced by 213 gallons. (Kinzey Pg. 21) There's two versions right there. Both B-29 and B-29A could have a four gun upper forward turret vs. the two gun upper turret. The turret occupied more space in the aircraft, was heavier but climb rate and performance were better than with the two gun turret. The 20mm cannon was deleted after B-29-55-BW, B-29A-20-BN, B-29-25-BA and B-29-25-MO because it was ineffective. (Kinzey, pg. 20)
the B-29B (668 were manufactured) was a stripped down version of the 29 built by Bell at their Marietta, GA plant. No remotely sighted turrets, louvered turbosupercharger well covers, third .50 added to the tail turret, AN/APQ "Eagle" radar (characterized by another wing between the bomb bays) and a tail AN/APG-15 tail gun laying radar (Kinzey pp. 24 & 25) Radar capabilities of aircraft in AH2 is moot so the main difference here are the lack of defensive armament.
Silverplate B-29's were special 29's built to carry the nuclear weapon. Similar to the B-29B, they were devoid of all remotely sighted turrets. They also had Curtiss C/S props rather than the regular Hamilton-Standard Hydromatic props. There were other changes as well but they did not recieve a separate designation that I have been able to find. These will most definitely NOT be modeled as I seriously doubt HTC would allow the carriage and use of an atomic weapon in the game.
I hope that if the B-29 wins, we get the version w/out the 20mm tail cannon but with the 4 x .50 upper forward gun turret
Kinzey, Bert. (1983).
B-29 Superfortress in Detail and Scale, Vol. 10, Part I. Aero Publishers Inc. Fallbrook, CA.