What will they be used for and how long do they need to be on each end?

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84 300D, 82 Volvo 244Gl Diesel

These will be used for mounting a Jeep Liberty turbo on a 617. It needs to be thread into the stock manifold 1/2" or so on the 10 MM side, pass through a 1/2" adaptor plate, pass through the 1/2" thick flange on the Jeep turbo on the 8mm side and have room for a nut. Say 1" on each side.

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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

You will need a good "Graded" stud for that.
Could the holes in the turbo flange be enlarged without making it too weak and just use a 10mm studs?

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84 300D, 82 Volvo 244Gl Diesel