BBCs are very tempermental regarding valve train. We've had PROPERLY prepared high revvers touch the pistons with all 8 exhaust valves. I always give them .120" on the exhaust if going over 7,000. It's a good "habit" to keep, in any case. The tiny loss of compression is far offset by the less perilous position of the valve.
Fly-cutting may be inconvenient, but it's worth the effort. A good automotive machine shop has the capability or knows who does. If the pistons are pressed and not "floaters", this complicates matters. A REALLY good machinist with a REALLY good vertical mill can do it with the rods still attached. Shops like ours use a "piston vise", that "keys" on the pin bores, and therefore can't have a rod attached. My mill is fine for the piston vise, but I don't have a good mill vise (not my "department")...
Vinnie takes a little different "route" but is essentially saying the same thing. Fix it, don't gamble. You have too much money tied up in it to allow a "short cut" to ruin it.
Two questions: Did you have "light" springs on the head during the measurements? Did you degree the cam prior to taking the measurements? If the answer to either of these is "No.", start over and do it with these as part of the procedure.