I recently inherited a 1970 Barracuda 340.  It is all original with matching numbers (motor, trans, body, interior, wheels, etc.) .  With a car like this, would it be acceptable to swap out the drivetrain in order to preserve the originals?  If so, what kind of motor/trans combination do you recommend tht would require minimal fabrication and cutting on the car itself?

That is a good idea. If your serious about doing that and want to keep the performance up Id go with a warmed over 360 . More common to find a 360 than a 340 motor. Keep the numbers matching motor and tranny in tact. You can use any 727 or 904 tranny and have it worked over as well.