I have plenty photos of M27's but my knowledge of trucks is lacking. What is recommended for the late steam era?
Before WW II, some M27s kept their original arch bar or Andrews trucks, but all the postwar photos I have (ten or so) of both single and double door versions show them with ARA cast steel trucks with integral journal boxes and spring planks. Closest HO truck in appearance is the Accurail "Bettendorf" truck.