What other headers would work on a 69 Camaro with a 350/350 combo? For example would headers from a 70 Camaro with small block also fit the 69 or maybe headers from a 70 Chevelle smallblock would fit?

You could look at various manufactures and see what applications are the same. The first generation Camaro's are Rear steer cars where as the 2nd gen Camaro's are Front steer. This means a BIG difference in Header fitment. I believe the 68-74 Nova's have the same rear steer subframes as the 1st gen Camaro, so that would be your best bet. Many headers have a hard time fitting all the 1st gen Camaro models, so good luck.

Good idea!