I have some notes on what I did to my AHM R-1d on my website:
http://www.faracresfarm.com/jbvb/rr/bmrr/steam.html#Models
It ran pretty well from the late '70s till the original gearbox
got too sloppy in the late '90s. Presently in the dead line
awaiting a round-tuit and some NWSL parts.
jbvb