What is a 42RH Transmission?

42RH is a hydraulically controlled 4 speed automatic overdrive based on a 904. Compatible, no, work has to be done to fit one in a Abody due to length and girth. They are typically behind 3.9 v6s and 318 v8 s so I’d say they are similar in strength to a 904. But can be built to handle a good amount of power.