[Excaliber]

Top oiler before Side Oiler, which came out in 1965 and I think '66 was the last year, except for "industrial" applications? A very rare and short lived motor to be sure. I would expect Shelby had access to the earliest engines available at the time. Possibly a "64" side oiler?

An interesting question:
How many and which Cobra had the side oiler? The comp cars I would think. Certainly the GT-40's that ruled LeMans! Easy to mistake a top oiler for a side oiler, they both have certain traits in common.