a quick note on garrett turbo's balancing method.
if you remove the turbo yourself, a quick check of the lock nut at the Compressor wheel will reveal all.
if this nut appears to have been shaved or ground down at all, then the Compressor wheel, Turbine Wheel, Shaft and Nut, were balanced as a complete assembly, then dismantled, set in the housing and thrown on a car!
if the Nut appears untouched by tool other than socket or spanner, then Garrett have used Turbine and Compressor wheels that have been individually balanced prior to assembly to the shaft, and no further balancing has taken place.
if the you find the latter, as i commonly have, i would have no fear of a mark and strip / rebuild method whatsoever, personally, as this is exactly what anyone else would do.
a professional company may, if they have the equipment, do a final balance check after reassembly, actually it is a harmonic / vibration test rig, but i'd be surprised if they find anything of significance if rebuilt carefully and as Garrett built it according to method 2 at least.
still up to you though mate, don't just take my advice, but i would definitely research wether the later turbo will fit first?
either that or dip your bread in my son, and pop that turbo cherry!!! lol