The RAC models were a really really hard casting (with the exception of some of the forged wedges) and you won't manage anything constructive without a full blown factory set up IMO. If you have such resources available you will be able to profile yours accurately anyway. If you are simply planning to use a twin profile 'groove sharpener' then (1) you are wasting your time (2) just use the end that gives you the best fit. It will almost certainly be the U (it is a U profile on mine).
I've yet to see a RAC face that doesn't look like it came out of the factory yesterday, once cleaned properly - mine are very old (RAC LTD model) and have hit thousands of range balls in their time but still look immaculate - even the white paint in the groves wears well!