RH10 head removal - modified open-end wrench?

I intend to remove the RH10 head from my 850 and replace it with one I got from Phil at Fair Spares and I'd like to have all the necessary tools with me since the bike is at my vacation home in a fairly remote area. I've heard that it's necessary to reduce the thickness of an open-end wrench by grinding it down to access two "hidden" nuts or bolts but I don't have clue as to the size. Can anyone please help?

Thanks!

wrenches

Greetings,
Its been awhile, but, as I remember the only wrench I had to modify (because I was too cheap to buy a whitworth set) was a 13mm box end. I had to make it slightly larger to fit on the one nut thats centrally located under the back of the head. Everything else was done with an assortment of metric and SAE wrenches and/or sockets.

GB

You need a ground-down 1/4" Whitworth (0.525" jaw) open ended spanner/wrench for the rear head nut below the carbs (number 2 in the tightening sequence*), and a long, thin walled 1/4" Whitworth socket or box/tube wrench for numbers 1, 9 & 10 (can also be used on bolts 3, 4, 5, &6). And a 3/16" Whit. (0.0445" jaw) ring or open ended wrench for 7 & 8.

*Tightening sequence: http://www.nortonownersclub.org/technic ... /head2.gif ("Play animations in web pages" needs to be enabled to see the tightening sequence, IE7).

As geo46er has mentioned, it is possible to cheat using 13mm metric wrench/box (jaws/inside faces need grinding) or 14mm metric (a bit loose) tools?