One V8 head, I highly doubt there is any chance there. They would be totally different. But I am only guessing on this.
Now a cut down 6 cyl head,. Humm,. It's not really worth the effort as you'd have to weld the end back on, get it all perfect and face the head again. The big question is whether all the oil and water gallery holes would match up?
If you want a really crazy idea, how about casting your own yellow terror head? Or even a cross flow head. Maybe you could convince Yellow terror to make one for you. hehe.
But luckily the stock heads not too bad anyhow. It's similar to the Blue 6cyl head ports wise.
It sure would be nice to see a starfire all done up. I wonder if you could cut 2 cylinders off a yella terra head and bolt it on. Or even more crazy, bolt one v8 head onto it.