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Luckily bloke up here is converting ls mitsubishi 140A alternators to fit efi 5 litres
120a alternator need upgrade power wire & swap pulley over
Did you take a look at the link? It appears to already have a v pulley to suit early VS 5L.
I already have a good rad, cabled in fans and welded up the rad to fit the fans so alt would be easiest at this stage.