Keep it #'s matching or swap?

[FlintTony]

Put the 307 in the corner of the garage. Build a nice 350 for it. If you ever sell, let the new owner have the 307 to put back in it if he wants.

[Hank70SS]

What Tony said, if you have the room to store the 307. Otherwise just get rid of the 307. Number's matching is important, sometimes but not always. If it was a true SS with documentation it would be important. Number's are important to Vette guys too but it's not that big a deal on a plain Jane Malibu,