When to, or not to rebore an engine

You might want to run the block down to the machine shop and have it checked first before making a concrete decision. Pistons for 273 as far as I know only come in cast and from egge.
2-bbl piston - http://www.egge.com/site/?d=43&dt=1
If I were going to do it. I would use these 4-bbl (commando) piston - http://www.egge.com/site/?d=43&dt=1

I would agree a 360 might be a better option for the part availability, performance and probably more economical also. It is a fairly straight up swap. Might need to change the torque converter as the early engine uses a small register or have a converter builder put the large register on yours.





There are no "number" matching until 68, however the date code on the block should be from 2 weeks to 3 months from scheduled production date of car.