That exactly what I did. Cut that upper tab off, mock it all up, then tack weld it while on the engine. Remove and weld it up. And yes, powder coat afterwards.
If I understand what you are trying to accomplish.... Get a stock one and fabricate it. You can get the geometry correct and keep it from sitting way to high.
I have a little more duration on the cam than you but did the same and it worked extremely well. Hydraulic roller Cam with Crower HiPo solid roller lifters. I used the PAC 1294 valve springs. To highlight others points, combo is extremely important. For a street application you want the lash on...
You will also need to fabricate a oil return line on the 4 bolt. I used all AN stuff, -10 line. Lucky I had some of the fittings and my friend had some other pieces laying around to help figure out correct angles. Built mine out of race car spare parts. :)
Just a heads up for the 4 bolt piece. I assume you are running a V band downpipe? I had to machine the OD of the exhaust housing so the ring could be welded in place. Here are some pics of mine....
I have run it with and without the EGR tower. You can trim the gasket if the EGR is not being used. The stock Plenum can be ported a lot. I might have some pics of one I did where plenum was port matched to a ported 62mm stock throttle body.