Reply to "Mangusta Hi po Engine"

You are not going to be able to tell if it is a 289 HP block by the casting number on the block because the casting numbers are the same. The only difference between an HP and a 4v is that the main caps are thicker. Ford started with the same block. Same casting number, just assembled and line bored machined with the the thicker caps. You usually can not just switch the caps over from another block without line boring the mains. They will be off a few thousands and will lock up the main bearings so the crank will not spin freely.
On the exterior you have a much thicker balancer on a HP vs. the 4v, the HP heads, which are unmistakable because of the screw in rocker arm studs and the cast in valve spring pockets that they have.
The only question is which versions are in there. I would think that they should be the '67 type that has the air injector bosses cast into the exhaust ports, and because it is a manual transmission application, the air injector "rails" over the ports.
The "service" heads all had the ports drilled irregardless of an automatic or manual transmission application but the heads intended for the automatic transmissioned cars had those ports plugged with allen socket plugs.
If it is the original distributor it will be dual point and the date stamping on it should fit into '67 production date ranges.
HP intake manifolds were iron JUST like the 4v intakes. Chances are the intake will be stamped from Detomaso like the 302 4v intakes were with and engine number on it.
There are two flywheel sizes right in this era. A 157 tooth and a 164 tooth. One is larger in diameter but the flywheel itself should be manually stamped into the engine side of the flywheel. The '67 SHOULD have the larger of the flywheels even though there are two bellhouses showing in the DT parts book. It might be that the first Mangustas used a 65 289 and it had the smaller flywheel so Detomaso was unsure of what "regular" production of his car would require and had service part numbers for both bells?
I believe that the original carb for that engine should be a 4100 with a manual choke.
Best to check each and every part on the engine to see what looks like it was original and what was not.
The FORD assembly plant attached aluminum tags on the bolt that holds down the dirstributor that has an assembly date and engineering number identifying the engine assembly on it. Most got thrown away by the first mechanics to "tune" the engine and set the timing because they were in the way. Some have survived. They also stamed the final assembly date into one of the pads on the front of the engine. It should have a two number and one letter identification. If it was going into a regular Ford production vehicle, by '67 the US Federal law required the engine to have the serial number of the car stamped into it. On the small blocks that was usually done on the pad on the block at the top on the back on the drivers side. Most Mustangs I've seen had a portion of the number stamped in and many did not have the last two digits stamped. Depends on which assembly plant did the chassis build. I would think the Mangusta engines came out of different source, perhaps directly out of the Dearborn parts depot and that was too far before the US assembly lines to conform to that stamping since those engines were not pulled off of the assembly lines to supply Detomaso apparently?
So many possibilities including having the engine changed in service under warranty?
In a Mustang the 289 HP would have had the special high performance cast iron exhaust manifolds on it.