Yes the injectors do plug into the head and the rail also bolts to it. You will need to plug the injector holes or leave the injectors in there with the rail to hold them in place. To solve the ignition problem you may have to borrow parts from another engine like a 22r and adapt them to the 5sfe distributor. The 5sfe distributor needs the ECU and the igniter in order to do ignition timing advance. Like you said MSD may have something that will work too. They have some great customer support too.
If you have the skill to build a custom intake manifold then you can eliminate one of the 2 most restrictive parts on the 5sfe, the other being the cams which you already replaced. Did you by chance build it with 3sgte rods and then gap your rings to 3sgte specs? If you did then you can spin the engine to higher RPMs and safely boost higher then you would without. What cams did you go with?
While building a carberated 5sfe is intriguing, there is also the option of running a piggyback which would not be nearly as complicated or expensive as an EMS. People have done as much as 300rwhp with the rev2 electronics, fuel controller, 460cc injectors and a 3sget MAP sensor. A 92 is rev1 though so you would want something with timing control as well as fuel. Just putting it out there. If you want more details on how to do it I would be happy to help.
I would be cool to see someone do a 5S-FT though.
