for me it depends on three things:
1- cost: my main case for saying that u should go rb over sr with that car, is that its gonna cost around the same
2- difficulty: ive never tore a motor down to internals, im sure its not THAT hard, but i would have to learn that as i go.
3- parts: i wouldnt know how to go about finding parts for it
so to awnser ur question “why not?”, it depends on those things above. but i can tell ur just being a dick.
why not vg30dett?
why not vq35?
why not chevy v8 swap?
my point is rb>sr