Interchangable exhausts with the 1979 KZ250A

I'm rebuilding a 1979 KZ250A twin and due to the age and metal quality of the original exhaust units I'm having a real struggle finding a replacement worth putting on the bike. I am quite happy to fabricate the mid pipe but getting that lip on the header pipe that engages with the exhaust locking collar to force the pipe onto the exhaust port is proving too much.
As a result I am looking to take a header off another exhaust system to use and I'm trying to confirm if all the KZ series bike of this late 70s/early 80s era used the same header type on 1.5" pipe or if the larger CC bikes used a different diameter pipe or a different header engagement system.
If anyone who has had more experience with these late 70's bikes or knows of an interchangeable header system from another model or even brand could advise I'd be much appreciative.

I did not see a 79 KZ250 in the diagrams at Partzilla. There's a KZ200-A2 which uses the same exhaust gaskets & exhaust pipe holders as a number of other Kawasaki models, including the KZ305/550/650/750 & other non-KZ models.

The header pipes on my 81 KZ650 are 35mm OD & they have donut flanges welded onto the tips that are 39.5mm OD.
From the info at Z1Enterprises.com the gaskets are 31 x 39.4 x 2.8mm. Z!Ent lists the same gaskets for the 200/250s.

Most 1980-on models have donut flanges welded onto the headers where they fit into the exhaust ports. I don't know how doable it would be, but instead of flaring the header pipe tip, maybe you could weld a donut onto the end & use shorter half-moon exhaust collars; or maybe cut yours down. ???

I didn't know those were all the same.
If you are having that much trouble and these work, I have an old set of 2 into 1 headers from an old late 70's KZ750B twin that might work.....The collector baffle section is black and the two down pipes are chrome....