The same chassis, some with a smoke unit and some without, was used on the 29X series, the 28x series, the 32X series, the 35X series and the 31X series.
Basically, any six wheel postwar AF steam engine except for the 0-6-0 PRR switcher will supply the chassis you need.
Some will not have the square for the eccentric crank, but that can be fixed with a jewelers file.
