The RPC #4 at Classic British Spares includes the part number 954/64 at the bottom of the title page.
The RPC #4 in the British Only Library doesn't include a part number, and the appearance of its title page is slightly different than that of the CBS PDF.
Other than those differences they appear to be identical in every way.
RPC #4 was updated and corrected by Triumph Service Bulletin (TSB) #12, issued January 10, 1966. TSB #12 presented over 43 changes to 1966 RPC #4.
See TSB 66-12
Download RPC #4 from British Only Library