I've seen a few Aussie capris running Haltechs, however the majority of folks don't modify their cars enough to warrant anything more than a
Rocketchip. There are drivetrain concerns that become a limiting factor that are not easy to overcome
Megasquirt has kind of replaced Haltech/Electromotive in the DIY market, as it can be tuned from any laptop anywhere by anybody who's done their research, as opposed to being tuned by a specialized technician. Depending on the version you buy/build, it's also significantly more flexible as far as what you can do with it. I have run a Megasquirt-II ECU in my XR2 before controlling fuel but not spark.