So a guy offered me a 90 5.0 for my Explorer I have for sale. My problem is it's carbed. He said the guy who he bought it from said it has more power with the Carb.I know this is not the case.It has got a holley street dominater intake and a street avenger carb and 268 comp cam, guide plates and new push rods for it all  in a box, it has an edelbrock performer on it right now and holley with msd, I am assuming factory Cam. In the pics of the motor it has the old style tin valve covers. Does a 90 not come with aluminum valve covers? That makes it a total engine swap, not a fuel system swap. 

  My point to him was that, in my opinion, there are only three reasons to ever swap out the factory motor. Someone pirated it for their hot rod and sold the chassis to some kid who got a 302 from a wrecker. Someone blew the factory 5.0 and got one from a wrecker. Unlikely, because if this was the case they would keep the FI and the valve covers. I think the most likely reason is it was a factory 4 cyl. In the pics it does not appear to have the 5.0 emblems. It is an automatic, were there 5.0 auto's?

    Is there a way I can tell, a question I can ask him to determin if it was a 4 cyl before? Should I care?

Forgot to mention he said it had a 5-lug conversion. Do the 5.0's have 4 or 5 studs? What about a 4 cyl?  

There is a letter code in the VIN that will tell you what engine came in the car from the factory.  The eighth character in the VIN is the engine code.  In 1989  (A) was the 2.3 liter 4 cyl (F) was the 5.0 liter HO         V-8.   Yes 5.0 HO mustangs were available with Automatic Transmissions.  From the pictures it appears this is a swap and probably won"t have the good internals,  Forged pistons, roller cam  etc.   I suspect the engine codes were the same for 1990 as 1989.     

Before i buy a car, I run the VIN.  Here is a free one:

http://www.kbb.com/kb/ki.dll/ke.kb.sp?kbb&35802&&carfaxshopretail&5450

You can also pay for Carfax and get some details on the car, but this one will come back with "'89 blue LX Hatch, 2.3L, 15 records on file."  You can tell if it looks legit or not but the important part is the motor, not an HO in the pic. 

I ran one the other day from car lot crusin.  The Vin came back as a GT and the car was in LX garb.  So that tells me that someone may have bumped it in front and replace the front and removed all the GT trim.  You never know until the numbers are run thru.

After completing a 4 to 8 swap, the car looks to be a four cyl factory fox. With no emblems, looks like a 6,000 rpm tach ( 4 cyl only), brake booster and vacuum tree resemble 4cyl material.

Engine looks like a non-roller cam, not an H.O. 

Looks like rear wheals are a four lug gt wheel.  If so, they only swapped out the fr. rotors for 5 lugs. On the rear, it requires swapping axles.

Sounds like a lot of cleaning up someone else's mess.

Good luck

It is a 4 cyl conversion. I am no doing it. The truck I was trading was on BC4X4 and another guy is giving me a pathfinder, a 91 kx250 and a 93 seadoo and trailer for it.  

besides the VIN a quick way of telling if it was a 4cyl car is the brake lines coming off the master cylinder. 302 cars had a couple of spiral bends in the lines while the 4 banger lines look like the ones in your photos.