I am not familiar with the G models, But it should be easier to use 617a parts, then to try to fit NA parts to the 617a.
The water pump on a G should be in the same position then on the sedans, means you can use the pulleys of the turbo engine for the water pump and alternator.
If the power steering pump mount is similar to the sedan then you can use the aluminum power steering pump bracket from a turbo engine.
Do you have the balancing disk in front of the crank on your 617a, the on held on by the 27mm bolt?
This part can not be exchanged between engines without re balancing.
Again, I don't know how much space you have in the engine compartment of a G wagon.
Some pics would be nice.

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76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.