You know while you have the heads off you might have them reworked a little. You could have them ported, new guides/seals installed and then have the chambers reworked. A little touch up in the chambers could give you a few more cc's and drop the compression back a little to be 100% sure that you can run on 87 octane.

Also, get some indexing washers and index a set of sparkplugs for the heads. I know this can be done with the heads on the car but you can get a better idea of what's going on with them off.

Abe