Hugh:
I am no expert on these facts or conclusions, but only piecing various details together. In researching further in the Carrera RS book, I came across a caption that confirmed Starkey's data that 911 360 020 was indeed "R2", and then another statement that "R1" was a modified 911S, 911 330 0789. Starkey shows R1 being 911 360 019, so that is one of my reasons for suspecting that 020 might have been a renumbered car also. One other piece of data that influenced me is that neither 019 and 020 have a conversion number, which would suggest they were not a normal production RS.
I have no data on RS s/n's 001 through 010 since they are not listed in the BOOK. I have wondered about those numbers, but have seen no source that lists them. Starkey's listing of prototypes does not list any of these numbers either. So, if you have some data on cars with these low numbers, I would very much like to see it.
I am very curious what the s/n is for the 72 that became #107 at the Targa (and was earlier #3 as Ernie confirms). That car is well documented in pictures as being a 72, but I really haven't seen any real data on the VIN.
At the 73 Targa race, Giulio Pucci destroyed both a practice car and competition car during practice laps, so the "mongrel" (which was probably a converted 911S) was upgraded with a new 300 hp engine and it was raced by Pucci/Stekkonig to 6th according to data in the Carrera RS book. Haldi/Kinnunen drove #107 to 3rd according to both the Porsche Sport 73 and CRS book.
Gib Bosworth
R Gruppe #18
Early S Reg. #434