As long as you transfer all the accessories such as the bellhousing adapter, starter, throttle linkage, etc. I don't see any problem with swapping engines. The serial numbers won't match, but the performance shouldn't change at all. If you've got a numbers-correct block it might be worthwhile to save it and have it rebuilt for future use.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!