There should be no way that it is actually streched. Nothing else holds the rear of the transmission/transfer case combination up except for the skid plate that the combination rests on. The transmission mount simply goes between them to absorb vibration.
However, with a little more thought, the transmission mount may now be a little bit too far to the rear since the spacer was installed. Loosen the 4 small 1/2" nuts in the center of the skid plate which should allow the transmission mount to move a tad on its own (or maybe with a little help from a small screwdriver to move it a tad) so it will be be in better fore/aft alignment with the transmission.