1987 ranger

So i got a ranger a few days ago. It was hesitating and really didnt have much for power.. So i changed the plugs and wires. Started running a bit better. After a few days of driving it i noticed it was running alot better. Lately ive been messing with it. Got a new air filter. While i was there i found out that the guy who had it b4 me switch out the engine. So we searched for the right one.

So now ive been trying to figure out what engine is in it. I know its from a mustang V6. I was wondering if anyone would know what he could have bolted into the truck.