Most who run the t25/28 bottom mount can run an SR downpipe from the dump with no issue. I cant say I know anyone with a Ka24-e setup though. KA manifolds have been made with T2 flanges for sometime now. Most of the KA24e manifolds I have seen in person are T3 flanged.
I had to make my own downpipe using two 180 deg bends and a V-band flange.
Short of going with a KA-T mass produced kit...... no KA-T is the same so there is no downpipe that you can just go and pick up
what mine looked like after I got done.
I did the turbo upgrade, jgs tools manifold kit and downpipe all in one day... so it doesn't take a lot of time if you have your own welders or access to a buddy or something. If I had done it over.. which I will when I go back state side. Ill slice it in have and divorce the pipe. Its Long as hell and I have to do a handstand to remove it.