What kinda exhaust flange do i need?

It is a weird exhaust exit, for a down pipe.

It don't look like a v band clamp.

Can anybody with a h2a turbo tell what flanges or how they made a down pipe?

Could i just weld a flange on?

 

Sure why not? The downpipe isn't as critical of a flange as the inlet is. It doesn't really support weight, and it's not exactly pressurized like the manifold-inlet flange is. I say go for it.