My ex-Hamburger SS/IA 340 Duster ran the Port-O-Sonic intake back in the day, apparently in its original combo.
When I got the car, it had a ported/polished Holley Strip Dominator on it, which appears quite similar to me.
Whether that was a later iteration of the car, or done in between by someone, I don't know.
The car was claimed to be the first 340 in the 10s - at one point 10.90 on an 11.08 index - and his deal was holding class records.
I went low-10s with the SD at 368" with the car - plugs always looked even, no lean/rich variation.
The car never saw street use, which of course is a different world, but was very responsive on return roads, FWIW.
I don't think the Portosonic was available when he first campaigned the 71 SS/IA car. I was in the process of building a SS 340 ebody and had bought a bunch of parts from both Hamburger and Cecil Yother. Ed told me to use the LD340 for a stick car and the iron thermoquad intake for an auto. I ended up not finishing that project because he told me that a 1970 Avs would not be competitive. I didn't want to start over with a 71 car so it became a street car. As a street car I tested just about every intake that was available at the time and ended up putting the iron back on and selling most of the others. I did keep the LD340 on the shelf for a while. This was before the Holley SD came out and maybe before the Offy. A few years later Herb M. tried to talk me into putting W2 heads and a Holley Strip Dominator on it but by then I was done with small blocks.
