PacwageoI was unable to confirm how Topre Realforce rows are labeled. The following Geekhack post was the best I could find, which suggests that they would be labeled "R4" at the top (function row) and "R1" at the bottom (spacebar row):
https://geekhack.org/index.php?topic=77576.0
However I believe that is the exception to the rule. Most commonly we see "R1" at the top (function row) and "R4" at the bottom (spacebar row). As one quick example, from the Nautilus drop:
search
So I think the safest assumption here would be to go with the common naming scheme and get one R2 and three R3, as Mudkipslaps mentioned.
emojiReading posts from others, I realize now that I was approaching this from the wrong angle. All that really matters is the labeling scheme used by the manufacturer of the caps. Whatever labeling is typically used for Realforce doesn't really matter.
Interesting side note, I was looking at my Realforce 87UB and noticed that the up arrow keycap is shaped the same as the caps in the Enter key row, even though it resides a row below in the Shift key row. So much minute attention to detail in Realforce boards.