Over the winter I bought the 904 DIY kit. Already had his RMVB in my 727 so just moved it over. Very happy with it. I think all told, I will have picked up 2.5 MAYBE 3 tenths going from a 727 to 904. I went to aluminum shaft, 300 more flash rpm on same dia converter and went low gear set. So it is not your TYPICAL 727 to 904 swap.
