Could go either way. There's always a purist somewhere that feels that you shouldn't modify anything right down to the spring clamps on the engine. On the other hand a lot of people buy 2wd blazers because they want to go low. Do the job right and it shouldn't hurt the value. Pull a hack job and sure, the value is going down the toilet.
You can always save the pieces that you cut out of the frame...tell anyone that states the notch is a dealbreaker that they can weld the pieces back in!
