fiat 131 exhaust manifold on a 124 spider?

[christos_s]

I have seen suggestions on mirafiori forum of using a 131 exhaust manifold on a fiat 124 spider.

Guy I see you sell some with the same suggestion.  Why would it improve performance over using the stock 124 manifold?

(1592cc Fiat Sport Spider 1973)

[guy moerenhout]

the one from a 131 will not fit .124 go down, 131 go to the rear of car .+_ 6/8 hp more