In reality, the Howell FI system is actually a GM setup with some modes.
Check out DIY FI
It has a lot of info on doing your own FI system.
I presonally will never have another veh with a carb (unless it's a classic...like the 67 MGB I have in storage). Once you understand the system...it's the only way to go.
I would speculate that your biggest problem will be adapting the TBI plate to your existing intake manifold and the dist. The nice thing about the GM TBI is that there is no crankshaft position sensor....the timing is physically set at the dist and the computer uses the pulses from the dist to determine when to fire the plugs.
Basically, you have the following major sensors that should mount to the engine with little or no trouble.
MAP - Manifold Air Pressure
Temp - Temp sending unit on the t-stat housing...or near it.
Dist - Connections to the dist (see manual).
There is some other stuff...mostly related to emisssions...like the charcoal canister...etc.
You also need to check your state laws regarding emissions. You might be better off getting a chevy SBC TBI motor and putting the whole thing in...
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore