Hi Larry,
Until one of our resident Navy experts jumps in and makes us all a bit smarter, you might want to visit a posting done by Ron Wood (aka Professor Wood...) back in June 2002 in the Early Lugers section, titled "Early Frame Tutorial".
Lots of great info...but I am not sure it specifically nails down your questions about proper frames for the M1906 and M1908 Navy lugers...
Thought you might find it educational until one of our Navy experts wakes up and sees your inquiry...
Regards,
Pete...