help ident these heads

I'm not familiar enough with 273s to really make that comparison. what are the casting numbers on your heads now? Those heads you're talking about may be open chamber heads. Your 273 probably has closed chamber heads. If so and you make the swap, you may end up regretting it. Maybe somebody can chime in who has more 273 experience than I. Why not just upgrade the whole engine? that would leave your 273 original and unmodded. Just a thought.