RevOD,, I have the same type of set-up you are putting together.
I just welded a 3" V-band flange to the flat plate. I also made the transiton from the turbine wheel to the 3" V-flange nice & smooth to the 3" downpipe.
Just so it would be easier to take off & on the downpipe.My flat plate has 5 bolts holding it on, so I did not want to takeoff all 5 bolts to unbolt the downpipe.
Now & can just loosen the one 7/16 nut on the V-band clamp & the downpipe comes off.
When you have your downpipe welded to your plate, be sure to check for flatness, they have a tendancy to warp after welding.
