will it work, can I have a flange made to adapt the 2.4L header (pacesetter or the like 4-2-1) to my 2.3L HO, since the 2.3L doesn't have a header for the 3rd gen J's yet? the runners look like they might be big enough and the outlet is at 3" IIRC, that should be big enough to make the proper amount of flow.

will I have to tweak the 2.4L runners to meet the exhaust ports on the 2.3L head?

you would need a 2.3 flange in order to do , i think the port spacing is close enough to make it work

the flange isn't the problem, I work at a machine shop
and I have the HO and LO mani (interchangable, just bigger ports) and can get the gasket at the local advanced auto. the 2.4L header is about half the projected price of the 2.3L one, and it's already made for our cars, that the big thing.