Power Brake Rebuild Questions.

[Thomas Wiencek <wiencek@anl.gov>]

I know that there were 2 sizes of power brakes used in the Alpines (5 in. and 7 
in.).  Were there any changes in the power brakes in each size over their 
production?  There is a circlip show in the Sunbeam Survivor on the back of the 
main (upper) bore.  My unit does not have one.  Missing or production change?  
Finally, does anyone have a good trick for removing a stuck main bore plug?  
I've tried pushing through the lever hole but the plug will not budge.  Thanks.
Tom