I would love to do 243 or 257 Robert's or 308. But are these even feasible if so what should I look for?
Yes, feasible.
Comparing your photos with my Model 70 short action made in Bridgeport not long before Winchester shut down the factory there, the inletting looks like it should fit. 7" spacing, the semicircle for the third bottom metal screw behind the magazine, and inletting in the trigger area (curved on right, flat on left) are all the same. I don't know whether they came from the factory in your preferred chamberings (mine started as a 308 Win) but should be compatible once rebarrelled by a competent gunsmith. You might also look at the Montana Rifle Co Model 1999 short action.
