i have been looking for a 2 into 1 exhaust header for my bike as mine is starting to crack and rust away.
do any other models fit the 750 like the 906,907i or other model 750?

All models mufflers fits but headers don’t,
750 smaller diameter.

Also the 750 cylinders are not as tall as the 906 or 907 so the heads are closer and the headers are not going to fit. A slightly larger header dia ( like 3mm -6mm larger) is cheap tuning . If you have the old headers as a pattern an exhaust shop may be able to bend up a new set .....maybe even in stainless. I have found that when headers start to crack no amount of welding up the existing cracks will stop the ones you cant yet see from developing further.
I made a header for my old suzuki quad and it was obvious that it wasnt quite right as there was a bit of stress getting it all bolted up / mounted , so I heat up the header at major bends ( u bend at ex port and kink around frame ) while still mounted untill just about melting and when it cooled it was a much better fit. I think the pipe sorta did its own stress relieving /alligning thing whilst nearly liquid.

thanks for the info, i will look into getting as set of headers made.

I believe that the European 750 header is a larger diameter than the US model.

there's a european and a US model 2in1 header?
For the stock 2in2 header it's correct. There are two different tube diameters but that only concers the part from the cylinder head to the cross. The tubes from the cross to the silencers are the same diameter for all Pasos & the 907IE.
If there's a 2in1 header for the 906 it will also fit on the P750, but as Hamish stated the header tubes are a little longer and the header may not sit right. I've tried to fit a stock 906 header on a P750 once and while it generally fits it shifted the whole exhaust system to one side. It may be less of a problem with a 2in1. However it's probably easier to find a 2in1 header for a P750 anyway. Rudy was selling two a while ago.

Hot tip , when fitting rear header pipe make sure its positioned ( there is a bit of wriggle room ) so the chain doesnt rub on header. Mine did rub (after I fiddled with it) but only on left turn in a high gear at low to moderate revs ...made a tinkling noise...I thought it was pinking but couldnt figure out why only on left curve . Drove me nuts till I saw the mark on the header .....still took a while for the penny to drop.

Speaking about 750P and 906 and 907 headers have to remember still one thing: 750 Pantah engine cant use 906, or 907 headers, as "lenght" of engine is totally different, so: 906 and 907 have samekind header pipes, but they dont fit to Paso 750 and via versa. I have tested that and measurements are different. Still: I dont speak now about 2-1 headers, but only normal header pipes !!!

Still to add to my previous post: I dont know ANY OTHER 2 to 1 headers, only that Conti 2-1 system what i have in my 907IE, but it DONT fit to 750 Paso at all. I think, You can contact to some Pantah / F1 groups, as they maybe know if there is also 2-1 system for Pantah engine and i quess, that there was.

There are 2in1 headers for the older Pantah engines but they don't have the reversed rear cylinder so the exhaust port of the rear cylinder is to the front.