I will admit to liking the idea of a 427 side oiler if only for the following 2 reasons. The bore spacing and bore diameters are larger, so technically better internal geometry within the engine. It is also a deep skirted block so should be more ridged. Looks perfect in a MK II.
Down sides, weight, length, exhaust port angle, head and push rod interference with intake, old, complicated design with lots of different things that have been improved on with successive engine generations.
for Lemans they only ran them with 1 carburetor on them, so they were unstressed and more fuel efficient. Reports at the time quote 650Hp as the output. Winning Lemans has always been about fuel efficiency and staying out of the pits, not outright lap time. same still applies today.
"The Cobra Experience" museum has a number of the engines on display with a few other intakes set ups. Dual 4 barrels, 8 stack set ups and the like. If you are not going to fit the same intake set up and same cam and heads, is it going to be the same engine and give the same results? you could just as easily get the same or better driving experience from a built Cleavland or a Windsor, that would be more serviceable and have less compromises in the car.