Hi there, this is my first post here. Just purchased my first "classic" car, a 1968 Cutlass convertible. After doing some research on the internet, I had determined my car has a 1974 vintage engine (according to the code for the intake manifold, 712753) if the information I found is correct. This site also had code information for the exhaust manifold as well. The passenger side manifold has a "4" (could not see the code numbers), and the driver's side is a "1" with the numbers 411961. According to this site, that make the exhaust manifolds small block manifolds. Now the previous owner had this car three years, and bought it from someone who redid the car, and he didn't indicate any problems with the car, and it runs good. Is this OK to have small block exhaust manifolds on a big block engine??