There are 2 heat risers (the flapper between the crossover and the right exhaust manifold) on ebay right now. Does a heat riser with the part number COAE-9A427-C fit my 1954 239 Yblock? How about B5A-9685-E? These are NOS.

Or does anyone have a good used one they are willing to sell?

Thanks!

 

At risk of getting in trouble with the number man, (a genius) the prefix C0AE would be for around 1960 and the B5A would be for a 1955, my books don't go new enough to say what the basic number / suffix mean (kind of).