[joe_padavano]

Headers for big block and small block Olds motors are definitely different and usually do not interchange. The exhaust flanges are the same, and the headers will bolt to the heads with the engine out of the car, but if you try to install big block headers on a small block, the headers will hit the chassis crossmember or motor mounts due to the taller primary tubes. Similarly if you try to install small block headers on a big block, you can run into problems with the tubes hitting the steering shaft and the heater box due to the shorter primary tubes. In addition, small block headers on a big block usually don't clear the bottom of the firewall.