Not as Hipo as it sounds. What's up?

I think that you should look into the compression issue. I put 360 heads on a 318 that had 10.5 compression and it brought it down to 9.2. They will bring a 273 down more since it has smaller cylinders. So whaever your compression is with stock heads, it will bring it down about 1.5 in compression if no milling was done.