As stated earlier, this vintage 327 originally sported GM Power Pack heads and a healthy 10.0:1 compression ratio-great back in the day of 75 cents a gallon 105-octane leaded fuel. But in this day and age $3-plus a gallon, 91-octane lead-free gruel is about all you'll find at the local corner gas station. To compensate for this and to take full advantage of today's high-performance technology, Barkley chose a set of RHS No. 12410-01 Pro Torker cast-iron cylinder heads. The new heads' 64cc chambers (versus the OE Power Pack's 60cc chambers) combined with the earlier rebuild's .040-over bore and lower (.040 below the deck) piston height effectively lower the engine's compression ratio to about 9.0:1-a bit more crappy-fuel friendly.