I have seen the later HR6 workshop manual for sale but I understand the bearing dimensions were changed. Is this the case?
The HA HB and HR6 all look very similar to each other but you are correct in that the the HB6 crankshaft bearing journal dimensions differ significantly from the HR6 (HR6 has a 4.25" cyl bore verses HB6 of 4").
I hope your fuel injection pump is OK as the HB6 has a unique governor arrangement on the the end of the in line fuel injection pump, which is unique to that application.
Sorry I cant help you with a workshop manual, but I am sure others will chime in soon enough.