Head Milled .050" - Which Grade?

There are too many variables to give a simple yes or no answer. Examples of the variables are altitude, engine maintenance, and load (weight). Second FT's advice, you'll need to tune it to your conditions.
See if this helps, section 6.13:
http://www.faqs.org/faqs/autos/gasoline-faq/part3/

Also, somewhere in there I picked up a rule of thumb that 1* of additional ignition advance or retard moves the octane requirement 1 point up or down. So if you move from 10* initial to, for example, 14*, add 4 points to the engine's octane need. Section 7.4.
Good luck :cheers:
 
running a higher octane gas isn't going to give you any more power by itself. All a higher octane rating dose, is it resists detination better then the lower octane fuel. Granted, a higher octane gas will allow you to run more timing, which means more power, but we are talking maybe 5hp, and alot more expensive fuel. I would think that you shouldn't be able to get by on 87, considering that you had the head milled, but if you can once you get the timing dialed in, then dont bother buying expensive gas.