Yes, I remember the Sundown well. Co-drove with Cam Champion in both 68 and 69 in his MGB. John Mann originally was supposed to drive with Cam in 68 and at the last minute I subbed for him - I believe the entry still showed Cam and John (Performance Cars of St. Catharines). Cam and I finished 4th o/a in 68 and 5th o/a in 69 - both times winning the small car class. In either 70 or 71 I co-drove again with Cam but in his Alfa GTV - I got out on the marbles in turn 3 and slid up the hill - soon to be joined by Craig Fisher in the Carter camaro! - so we ended up dnf.
Mosport was a great track to drive - especially in the dark! I remember the MGB handled very well, although not much power. I believe it won the E prod. title in 69.
I understand the 6 hr. has been revived but in a shorter length? Hope it continues on.