I never saw a wagon, although I did hear of 'em being used. I think it must've been a regional thing. Most of the sleepers I saw were the land yachts I mentioned & perhaps the best of 'em were mid/low 11-sec. cars when sprayed, although my friends Impala was quite a bit quicker than that, but that really was a racecar more than a yacht.
There was a guy herein Phx in the late 70s that had an late 60s Caddy, Caddy-powered that was good for low12s/high 11s. It was the first time I ever saw a 2 4-bbl set-up on a Caddy motor--really a pretty neat car since it wasn't "cross-bred....