Bob's Resource Website (2007)
Hot Rod article R3 Lark 1964
(incomplete, but it appears to verify a 1964 R3 "Lark" was produced)

Could it be the one advertised in the April 1985 Turning Wheels classifieds:

1964 R3 powered Daytona Hardtop Super Lark:
totally rust free California car. 68,000 miles.
Powershift 3:54 TT. Bordeaux Red; Black
reclining bucket seat interior. Two-time SDC
National First Place winner. $8000. Price
includes an original R1 engine. May separate.
Ron Hall, 302 Richards St. Geneva, IL 60134.