Since no commercially-made manifolds exist for the S-U setup, it would be a one-off fabrication job. Anybody handy enough with a milling machine, aluminum billets, and a TIG welder could probably make the clearances work. The engine compartment on the Jag was at least as crowded as under a Stovebolt hood, probably more so. I'm planning something similar if I get around to running a 230 inline six in the Excalibur roadster I'm building, with three Weber DCOE 40 side drafts and enough internal modifications to run a 6500-7K RPM redline.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!