Proper Exhaust Diameter fo a 4bbl 225?

Slugfarm said
The machinist the mechanic uses is going to do a .100 shave along with the port work. Once I retire maybe I can get on as an apprentice there and finally learn some of this stuff myself.

That's what I intended my current head to get milled. However, a mishap occurred and it had to be milled a lot more to straighten it out.