It's not between the block and the lower housing

It's between the lower housing and the upper housing as shown in the picture 

Pete will tell you to find a new mechanic as well 

Do you have a IR temperature gun or can you borrow one? I ask because I suggest getting a true temp right at the T stat housing to confirm the running temp.

cant get the photo to appear    dont know why    i was able to post a pic before under  throttle cable thread    now i cant upload pics of my thermostat housing which does not look like the pics you guys posted      can i email pics to someone to post them?

You can email me the picture and I will post them. I'm going to work shortly so I may not get to it till later. Ken's around all day so it may be better to send them to him?

Here's a link to my email:

mailto:petebrainard@att.net?subject=pictures" rel="nofollow - mailto:petebrainard@att.net?subject=pictures

Pete  I'm feeling a little violated here with you knowing what I may or may not be up to 

Jerry   you could e mail the pictures to     keno439@gmail.com     and they'll get posted here

PS the picture of a little bit of the engine in your throttle cable thread says "it's not a PCM" or at least the external things like the alternator and exhaust manifolds aren't.

I may be busy for a while tracking Pete's movements, but they'll get posted 

Here are Jerry's pictures of the engine

I think it's a bit of a mixed breed pound puppy. 

I do see some Interceptor wording on the timing cover

The tag can be deciphered fairly easily.

By 2003 a PCM Ford engine was a thing of the past unless it was a stockpiled replacement engine, but there is a lot of non PCM stuff bolted onto it like I mentioned.

Also, the distributor is a clip down cap Prestolite that they quit using in 1986 but my x ray vision says there's an electronic module under the cap. I'd say that's a good thing 

The fuel line looks to be a combination of rubber and maybe steel in the pictures.

Not picking on the engine, just pointing out some stuff that is "out of the ordinary" and trying to help you figure out what you have  

You can click on the link below and look at the pictures of the front of the Interceptor engine for some similarities to yours. 

Here's a picture of the front of a 351PCM for comparison

Here's Jerry's engine tag

I'd say it's from a 70's or 80's Pleasurecraft 351 engine since they were located in Ohio in those years and it's reverse rotating and by the early 90's reverse rotating engines were pretty rare and PCM had moved to South Carolina.

So my guess is somebody took a PCM engine out of a CC from those years and bolted on all the Interceptor stuff, sorta half keeping things original  

He did mention that he's not exactly a "keep it original" kind of guy but that's OK 

 Nice to say the very least!   I have a sound feeling you will do a fantastic job on the Mustang.