Turbo D4D ?

David - Before your friend commences his upgrade to a turbo, I trust that he's aware that oil-cooled pistons are a necessity for a turboed engine .. and if his engine is not already fitted with them, he would be well advised to fit them.

Additionally, increased fuelling adjustments need to be made to take full advantage of the extra air .. with possibly bigger injectors.

I'll see what I can find in the engine specs microfiche as to turbo numbers fitted to the turbo engines.
Be aware that governor springs are often changed with turbo engines, and also, that increased water and oil cooling may be required, if cooling is already marginal.

The blocks are all drilled out for installing the tubes but if they are not needed in the case of a natural aspirated engine then there is a blank plug in them so when the turbo is used then the tubes are part of the block.The crank usually has to be removed to get the plugs out then the spray tubes are driven down from the top side of the block bearing bores.Parts books for both style engines will need to be gone over to compare parts & what needs changing for the turbo setup.It,s not just a job of slapping the turbo & manifold on from the outside but needs some serious checking of everything involved so down the road you don,t get in trouble.