Were the stickers produced by Ford or the dealer? Surely if Ford made them they would have put the Ford logo on it.
This is from wiki
one of the first 50 engines which was in a RS 3100 that was free for car magazines to review and test in fact had 165 hp (123 kW; 167 PS) instead of the 148 hp (110 kW; 150 PS) of the rest of road going RS 3100s....
Also Jeremy Waltons book states pre production RS3100 had 165HP due to cam and exhaust mods and that these mods were expensive and never made it into production, and that the RS3100 was quoted at 148HP, page 58.
So maybe the dealer made the stickers and maybe they got the 165 figure from a review of an RS3100 thinking that it was the same engine???
If we use consistent units then I think its safe to say that the early capris were 128HP, the RS3100 was 148HP and the BSS were up to 138HP depending on if all the mods were included such as weber 38DGAS and viscous fan.
In any case it's highly unlikely that they were a genuine 165HP.