I haven't 86cobra in some time, he probably had the most powerful NA 306 i've seen in any forum. IMO, you can't expect to duplicate his numbers, yes it could happen and would be great, but i wouldn't count on it.
And i believe his heads were TEA motorsports, cnc wedges.
On a 306, i'd just use the regular wedges with some mild work, bowl cleanup, valve job, springs. Then use a custom cam, rpm intake.
If you feel that the car truely has more in it, or get a stroker, you can pull them off, cnc them, and sell the rpm intake for a II.
Or, just scrap the 306 idea, make it a 331 or 347, then use the cnc wedges with the rpm II, it will be a beast, probably a mid 11 car.
And sorry, a 347 that runs 115mph, is not the fault of the driver or the gears, it's the engine. Figure if it hooks, the time will go down, but so will the mph.
I know guys that have cracked 115 in street cars with stock shortblocks.