Wow. Turns out that in 1968, after Jerry Lee, but quite likely pre-Kenny (because black musicians weren't exactly known for ripping off the whites back then, if you know what I mean), the song was actually covered by soul singer Bettye Lavette! Fantastic!
There is also a great dark country blues version by Mickey Newbury, the guy who wrote the song, a year previously! Jesus! The chord changes for the song, by the way, are here. Not quite sure if that follows the Newbury version, but in the absence of a horn section, just give it a dark country blues feel, and you'll make out okay!
(By the way, since that song was allegedly written as an anti-LSD song, check out Larry Norman's "No More LSD For Me" as a follow-up course - not quite as good as "Six Sixty Six," but... I mean, doesn't it sound an awful lot like Daniel Johnson?).