Score! What did I do?

Sounds like a nice find !

If you want to keep the 273 - go smaller on the cam. The extreme 268 might be bigger than the 273 can handle, my guess. Depends on what you are planning. For quickie swap I'd do something like a 340 stock cam, get a computer engine dyno simulator and run some different combos. You want to try and keep your torque band lower with the small displacement assuming you have stock gearing etc.