the older style fast before this new stuff requires a bit of work and tuning.
the self tuner....work pretty good. if your happy with a carb you will be happy with those. i have installed both, though not recently in rangers.
you may consider putting it on the dyno to help diagnose the bog with the 4bbl. may need a bit of a timing adjustment or maybe move the cam around a little with a rollmaster if you dont have one installed already. the 347 make quite a bit of torque compared to a reg 302 down low, but seriously a stroker 351 is ideal for your use. i run heavily loaded as well in the general and a reg mild build 302 with efi was always working pretty hard. the 351 is a different beast all around for work.
of course your trans and split shifting are harder to match with a carb as well. those old creeper transmissions were made for low rpm nutless no power pussy engines. if you like a 435 or t18/19 trans in stock form on the street...your engine is a bitch. at least with overdrive splitting you can actually use your engine.
so the efi might not impress you as much. i know i would prefer the efi regardless. you dont get as crazy as some of us so the 4 bbl is quite usable and hard to justify the cost of the efi upgrade. but it will be a upgrade. i can not see any performance lost at all....simply maintained or gained in every area.