906 or 915 ?

The castings can vary quite a bit from the factory, but for examples where the valve job isn’t total crap, 906/915 heads with no porting typically flow in the high-220’s to mid-230’s.
Untouched 346/902/452 heads are less likely to be in the 230’s(but, IMO are easier to get into the 250+ range....... without having the numbers crash in the upper lifts).

270 from a 915 wouldn’t be an all out job on my bench either, but noticeably better than what I usually see from a home ported effort.
I wouldn’t mind doing some clean up at home but I would think you would need flow checked constantly to get equal readings from cylinder to cylinder..how would one do this