Here is the car chase scene in Brewster McCloud (1970). It takes place in Houston, TX. I am curious what streets are shown from 0:46 through 1:06.
At 1:06 you can see the name of a street at the intersection (Fannin St.) and a sign pointing to the “Domed Stadium.” Fannin St. is a north-south street in Houston. The red muscle car is traveling on Fannin St., and then takes a left at that intersection. A few seconds later, a Trans Am travels through the same intersection on the east-west street, chasing the red muscle car.
I am curious where this intersection is. One problem is that I do not know the name of the east-west street; I only know the name of the north-south street (Fannin St.).
I looked at major roads that intersected Fannin St. on Google Maps, but none of them look like the movie scene. My best guess is the scene takes place at the intersection of Fannin St. and Old Spanish Trail. If so, I am amazed at how much it has changed.
I think you are right. At the start of the scene the red car goes through a 3-way intersection with a triangular island, that is just south on Fannin St. You can see the aerial photography of this area by going to Historic Aerials: Viewer and input the road names. They have aerials from as early as 1953 including 1966 and 1973.