67 GS400 Wildcat 137139 exhaust manifold

Guys I just noticed on a 400-430 motor I got sitting in the corner. Its got a 67 137139

https://www.teambuick.com/reference/images/casting/1377139.png manifold on it.. I know its rare since its a 1 yr only....
My motor in my car has a newer 123451

https://www.teambuick.com/reference/images/casting/1233451.png it.....
I got a tiny exhaust leak now I can easily just loosen the bolts and slip in a set of gaskets and be done. 59 minute job..

Or is there any advantage to using the 67 over the newer EM. To me just on outside appearance the 67 has a cleaner flow.. Is it worth the work?

 

One of the 67 manifolds does flow better

 

Thanks SBM.. I thought I saw that before.

Heres the results of the dyno.....http://buickperformanceclub.com/Exhcompare.htm

Not going to be to hard to swap. I'll just swap in the tilt column at the same time.

 

They are prone to crack

 

Had a feeling about that..... 1 year only stuff...