it is for a 1973 ford f150
This conversion will require a lot of parts in order to work properly. You'll need to find the same engine at a junk yard with a throttle-body injection (TBI), since basically TBI is a glorified, electronically-controlled carburetor. However, you'll of course need to scavenge the computer guts as well as the air intake (with appropriate sensors) and intake manifold (as the throttle-body will not directly bolt to the old one), the EGR valve and vacuum lines, and you'll need the exhaust manifold with a port for an oxygen sensor.
Depending on the year (the newer the engine, the more complex the system) you may also need to figure out whether you need crank positioning sensors and such. It depends largely on what the computer needs to know in order to calculate the best air/fuel mixture for the current RPMs and load. Sometimes you can skate by without certain things as the computer may be smart enough to plug default values into non-existent sensor readings, but it could also keep the engine from starting all together, or cause rough idles, stalling, and so forth.
I can't get into specifics here, so a search will do you some good, but I can tell you this isn't as easy as dropping a TBI where the carb used to be. Be prepared to tear that engine down as it certainly has not been designed for any sensors whatsoever.
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I'd say find a complete engine from a '90s-era vehicle and all the peripheral stuff needed under the hood for it to run properly.
As I recall from my 91 S-10 Blazer, You'd need the unit itself, plus all of the sensors and controls it uses.See this wiki link for more info on the required components. (scroll down to the section entitled "Detailed function)
Note that if your engine is standard issue, it might be more cost effective to hit a junkyard for a later model, wreck with a comparable engine AND EFI already implemented, then swap the engine and scrap the old one (after cannibalizing it for things you might want need in the future of course...)
You'd buy a full kit I guess. You need more than just the carb' replacing, how about finding a Ford forum and looking around there?