The only real difference between the soft dash used in the various 1200 models is the colour. Earlier ones were black & later utes were brown. If you have a good ute dash but want black then some vinyl dye should do the trick. The coupe had a different instrument panel to other 1200 passenger models & this design was adopted by the ute after about 1976 or so. Not identical, but almost, as the colouring is slightly different & the instruments have more colourfull face markings.
Since the soft dash is the same for all, these instrument panels will interchange.

The 1200 GX coupe & the later utes use the same basic grille. The only difference is the colouring with the GX grille being all black except for the perimiter around the grille opening.

Have a look through Ddgonzal's photo album as I'm pretty sure that he has GX grille pictures in there, so again, that part at least should be fairly straightforward with the conversion of a new [or old] Ute grille being done in a spray booth.