That "dent" is there for a reason, it's to accomodate the crossover pipe on an RB25, check and you'll see what I mean.
As for the Gates belts, yeah, they whine, comes part and parcel of those belts I'm afraid and it's well documented.
If you're going to get it ported, go to Rhemac, speak to Mark. They are the guys to see, do awesome work, reasonably priced, know their shit and best of all, right here in SA! They did my 26 head, came up sweet!