Ford RST EFI fits mostly plug&play to a N/A EFI but like you said, these are getting old, sometimes don't work properly nowadays and there's not many people out there with sufficent knowledge.

I'd also go for a modern standalone management. Either one you get basic RST maps for or one that is used by companies who have done a few RSTs before. Just keep in mind to change EVERY sensor and the injectors as these usually don't work with an aftermarket management. The CPS probably will work and you can keep the sensor for the engine temp gauge.

You can keep the head as it is. When it comes to cams there's a lot of different opinions about them. Some say keep them standard and turn up the boost a little bit more. Power plus a smooth running engine on low revs.

EFIs came with a compressoin of 9,75:1 while the RSTs had 8,3:1. So you will have to get turbo pistons. Standard ones are usually ok for about 180 hp. For more, get a set of forged ones. And you'll need an oil feed and return for the turbocharger.