Yes, and it worked wonderfully. Both performance and gas mileage improved.

The intake (and recommended carb) were targeted for specific type of application and did well in those applications.

If you are starting with a factory high performace 4 bbl application and the goal is more power, you simply would not choose a SP2P as that is a complete misuse.

What was the vehicle and engine? What carb did you use with it.

A Mirida. 318 2 bbl.

I don't remember the carb specifics, but it was something like a 450 cfm 4 bbl. It was not a typical spreadbore, but the primaries were pretty small relative to the secondaries. It had real nice throttle response too.

Your carb was probably a Holley Economaster unit.They made a 450cfm,I had one on a 1976 Cordoba 400,it ran well actually with that carb,stock engine.

Boy intake manifolds made in the 50s seem to show engineering much far behind the 1970s. For example- Offenhauser- their manifolds are just a big plenum with a divider and thats it. Single plane design but not the legit single plane design as say a Torker TM7 and Street Dominator (All 1970s designs). Offenhauser and Weiands dual quad intake looks like they copied the mopar factory 413 dual quad intake. Nothing like the Edelbrock tried and true dual plane design. Im sure the compromises I mentioned are in that old single carb 383 intake you have. A used Performer (idle to 5500rpm) can be bought reasonably maybe cheaper than an OEM 1971 ish iron intake.. Id run that and be done.

years ago [around the 1982-83 ish time period if i remember right] i tried a split plenum single plane intake. i made the divider from 1/8" aluminum plate, and put a couple of locating notches in the carb flange to hold it into position. the "butt dyno" said i made an improvement, but i think the time slip said different.
i didn't spend much time trying to sort it out, so i can't say if it is something worth pursuing or not.
anyone else try this, and if so, what were your results ?