They will fit the bore but you will have little power because the wrist pins are cast lower in the piston on the 292 than on the 250. This makes the 292 piston not only taller than the 250, but a "taller deck" piston as well.
The much lower TDC height of a 250 piston would give you fewer than 292 cubic inches and, I'd imagine, much lower compression than a stock 292 (which was a rather low compression engine as is).
-magic mike-
