Both... for all intent and purpose a 302 is a 5.0.
For a BII I'd start with the engine and acessory package from... an Explorer. (Didn't see that one coming did ya?

)
Seriously though I would recommend the engine and acessory package from the Explorer whether you plan to car it or not. That one has the tightest acessory package of any factory 5.0L and the 83-92 Rangers and BIIs had the tightest engine bay of any RBV.
From there decide which ever works better for you. You could adapt the EFI system from the Explorer donor. Install a Mustang based EFI system, prety much all parts van be bought new aftermarket. You could go full aftermarket EFI using the factory EFI intake. You could drop on a carbureted intake and and carburetor, or spring for the Sniper.
FYI Sniper isn't really going to add any power over a properly tuned carburetor, however most caruburtors that they replace aren't properly tuned. What the Sniper does do is allow for automatic adaptation to various conditions rather than having to tune the carb to account for them. I've done it on an old truck. It isn't pretty but it works well and the whole truck needs rewiring anyway.
If you want to avoid wiring Sniper is probably not for you either. While there are only a few wires to actually connect (depending on options) there are a lot of wires to route and they take careful planning and consideration to avoid any EMI related issues. I would say it probably isn;t much more difficult to install the factory mustang based EFI systems, or to convert the Explorer system to standalone. I actually did the latter once, it wasn't difficult once you dig into it, but I never actually got to the point of testing it.
If going EFI the plus side to a factory system is obtaining replacement parts and they do have some diagnostics capabilities built in if you take advantageof them.