I found this pic of the unit out of the car which shows how we modified the original intercooler as I did not want to cut up the car.
The 3" pipes are actually from a Ford PS diesel truck, and only rather simple mods were made to use them on a Buick!
I used the PS on my race car for years before I stepped it up and replaced it with the RJC mega-intercooler. The data logs did show a slight decrease of air inlet temps over the PS at the end of a pass, but they were very close.
A friend had a Precision FMIC at the time when we were racing, and his inlet temps were higher by 30+ deg.
Another GN with a similar build had a V-4 stock location IC and he would run 50-70 degrees higher at almost a second slower, meaning much less HP.
One of my street cars with AC and the PS intercooler is a low 10 sec ride, and during the summer in 105 deg. weather the coolant temp runs at less than 200 deg. at highway speeds which is about the same as a GN with a large stock location IC.
The basic design of the PS is very efficient, and the large area will allow lots of airflow for good efficiency of the IC, and still lets the radiator get ample air for cooling as well.