You're pretty much screwed. Sorry to be so blunt about it, but it's true: the '91-'96 Chevrolet Caprice and similar-year Buick Roadmaster and Oldsmobile Custom Cruiser have
awful headlights. The European version wasn't better than the US version, just different and still severely inadequate. GM went from a quality, very high-performance headlight system on the '87-'90 Caprice, to this cheap and nasty junk on the '91-up models...perplexing until you remember this is the kind of thing GM does, routinely.
Of course there are all kinds of toys and games available, marketed as "upgrades" with clear lenses, projectors, LED arrays, etc. All with the durability and performance of a 49-cent "Rolecks" watch bought from some guy named Slide in a back alley. Unless you're prepared to build a custom solution with headlamp modules (Hella 90mm or similar types from other makers) and a fabricated bezel, along the lines of what
Morette used to do, you're stuck with what GM offered.
Make the best of it by making sure everything is in tip-top condition. That would mean new genuine GM headlamp units -- no longer manufactured, but still findable for example
here and
here. Wire it up with a relay setup from Dan Stern or another reliable vendor. Put in
the best bulbs available, and make sure the lamps are aimed carefully and correctly, either with a mechanical aimer (the kind that interfaces with the three aim pads on the front of the lens) or an optical aimer -- not using a slipshod "shine them on the wall" method.
All of that will make them better. They still won't be great, but they'll be livable.
As far as the taillights go, there are no "T84 spec taillights". T84 is the GM code for ECE headlamps for right-side traffic; it has nothing to do with taillights or anything else. The codes for export tail/stop/turn signal lights were T89 and T90. There were export tails for these wagons, but it will take some extraordinary luck to find any of them. They had an amber-lens turn signal section at the bottom where the home-market lamp has the reversing light, and the reversing (and rear fog) lights on the export cars were in a clunky, ugly housing thrown onto the tailgate or rear bumper. Putting amber bulbs in the reversing lamps does not convert them into turn signals; the two functions have different light distributions. If you are dead-set on having amber turn signals on this wagon, you could maybe see if
this guy in Australia could make a set for you based on a set of US lamps sent to him. You'd want to leave the reversing light where it is and have the main lens half red and half amber (or I suppose it could be half red and half colorless and you could use an amber bulb in it). There would need to be a separator plate added between the brake/tail and turn signal compartments so that you don't get light bleeding over from one into the other.
The car does have combined brake/turn signal wiring, but that's not very difficult to overcome, it's sort of the least of your troubles.