[Healeys] Distributor Caps

[PhilRitten at aol.com]

All,
 
I'm interested in getting a replacement cap and wires for my '58 BN4 (and  
my '61 BT7). I'm looking for the type that plug in so that I can more easily 
 swap them in and out. (note I currently have the plug in type)
 
When I go to the Moss website, they say that the plug in caps (#560-125)  
only work on "Late BJ7/BJ8 (25D6 Distributors)".
 
Question: Were the later distributor caps/distributors a different size  
(i.e. larger diameter) than the early ones?
 
My apology in advance if this has been previously discussed.
 
Thanks,
Phil