I don't know what to say, except that I would use the one in the best condition (bearings not loose, blades straight, etc)
I did find a link to the various makes used:
MERCEDES BENZ
MODEL YEAR ENGINE DESCRIPTION TURBOCHARGER
300 SERIES
1978-84 3.0L I5 120HP @ 4350 TA0301
1978-84 3.0L 3.0L I5 KKK VERSION K26
1985 3.0L I6 TA0310
1985-87 3.0L I6 KKK VERSION K24
1987 3.0L I6 TB0369
1990-94 3.5L I6 TB0369
source:
http://www.hardlineturbo.com/APPLICATION%20TURBO.htm
Incidentally hardlineturbo sells kits, I believe the Garret TA series runs $90 for a kit, as always check with the web site for more details.