Back when they were new (yes, a few of us remember that!) "Power Pack" was an advertising buzzword for a 4-barrel engine with high compression heads. There were all sorts of factory "go fast" options (camshafts, etc.) that could be special ordered or dealer installed. The heads with a triangular shape on the ends had 58CC combustion chambers. If you find a set of those heads now, they've probably been rebuilt half a dozen times, or they're worn out to the point they're going to need new valve guides, valves, and possibly valve seats. Fortunately, they're not prone to cracking, so they can be reconditioned pretty easily. If you're not particularly interested in a "numbers-matching" engine, 58CC 305 heads give the same compression ratio and they have better valve size and port shape than the original heads did.
Jerry
