I am thinking to swapping my 91 5.0 engine in a 86 Mustang GT automatic I know the 86 Mustang was the first year the EFI engines can out but I am not sure if my 91 engine and the computer will fit in the 86 Mustang?

 

of course it will. You will have to use a 86 oil pressure sending unit and temp sending unit for the gauges

 

Too many double posts by all these noobs lately lol.

 

The EFI system on the 86 was only used for one year, with major differences from 87 onwards. Check this out thorougly before proceeding.