Switch on dash to change between gas tanks

[Paul C10]

I recently brought a 1974 Custom C10 (RHD) (I'm from South Africa) , it does not have the black switch on the dash to change from the one gas tank to the next. (Previous owner did install a manual switch under the bench seat) I did get hold of the switch from a 1978 C10, what is the process to install that ? Also I want to install the 1978 Headlight bezels & grille to the 1974 C10, but some of the guys informed me the 1974 grille & bezels are the best , what is the general view on this ?

Lastly does anyone in the US have any data on the 73 - 80 Trucks assembled in South Africa, I cannot find any info. ( I know they were assembled by GM SA from 1974 - 1980) It seems a lot of the parts came from Canada, because GM Canada is stamped on a lot of the parts. Would it help if I supply the VIN Number ?

Thanks

[VileZambonie]

If the harness is there just plug it in. I like the 74 grille and bezels better than the 78 but that's just me.