Ummmm......Help?

I have an all-original, untouched, factory made 1942 Daimler-Monotype Mk II, so we'll get that part out of the way so as not to bring up questions surrounding "....is the receiver in spec?" Yes, just the way it was manufactured in 1942. NEVER touched. This gun has not been altered in any way since the day it was finished in the factory. (yes, of course, it is a machine gun...)

So, I have an L4 magazine adapter-ejector block I want to try and install for experimentation purposes.

It is just a RCH too wide along the sides to slip into the Mk II receiver mag well at the rear end.

So, my question is- during the course of the MoD-ifications to these guns originally when the L4 program began turning them into 7.62mm guns, did they "open up", i.e. machine away any portion of the inside rear area in the .303 magazine wells??

If so, is there a dimensioned drwg or print of the machining to be done at this location?

THX!,
- TomH