The problems with the 273 is they have no compression, the bores are to small for bigger valves and the stock heads dont flow very well. I had a 273 in my barracuda and asked the same questions. I had the bottom end rebuilt with stock replacement pistons as custom pistons were in the 600 dollar range. They were .050 down in the hole and were spec. at 8.0 to 1. I had the heads angled milled to a closed chamber to raise compression, and gasket matched the intake and exhaust. The motor ran good for a 273 but I wanted more, so I am putting in a 340\ 373 engine. Looking back I think the money I spent on the 273 was a waste for me. Some other members have 273 that run really well, maybe they can help you more. I still have the 273 heads if your lnterested. I can email you some pics if you want. Bob
