There were a few turbo kit manufactures for the 616 back in the 80s. As long as you keep the boost down to 5-7 psi and keep an eye on your exhaust gas temperatures it should be OK. Like has been said it is still probably less expensive to just put a turbo 617 in like I did.

Here is one kit that used a variable geometry turbo: http://www.hiperturbo.com/other_application.htm

You could try to contact them to see if the kit is still available. Kits with standard turbos pop up on ebay from time to time.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine