retrofitting non-cat manifolds to later models

[Dave80GTSi]

I did a search on this topic, but did not find anything.

The later model 986 exhaust manifolds with integral cats are a flow horrorshow. See enclosed pinch point, shown in second picture.

Putting the differing oxygen sensor location issues aside for the moment, has anyone ever retrofitted a later model (like, just for a random theoretical example, a 2000 S) with the exhaust system from an earlier model 1998-1999 or so non-S model with no-cat manifolds?

My question centers around whether or not the early non-cat manifolds (first picture), combined with their complimentary secondary pipes which run from the manifold outlet flange to the rear muffler inlet, are dimensionally interchangeable between the early no-cat and the later cat models.

Is it all just a simple bolt-on?

Thanks - DM