the 4.6 aluminum blocks manufactured from 1993-1998 and some 1999's were manufactured in Italy by Teksid. these were a very expensive block for Ford to have made and are probably one of the most durable blocks produced for the 4.6. these blocks are very desirable among racers. these blocks can be used for any 4.6 engine build with any of the 2valve, 3valve or 4valve heads including Cobra R heads.
the strongest Teksid block produced of that vintage was the front wheel drive block in the 4.6 Lincoln Continental due it's added ribbing in the sides for it's East/West fitment in the FWD Continental. motor mounts become difficult with that block but the added strength makes up for it!
most of the aluminum and cast iron blocks can all be interchanged for whatever application is needed. special attention needs to be given to Windsor iron blocks which have a big "W" cast in the block. while some say it's a stronger block, some problems can occur when installing the timing cover. it's possible not all bolts will line up on the Windsor blocks. (usually not a huge problem)
The newer aluminum blocks can be used in an earlier applications by simply drilling out and re-tapping the knock sensor holes in the valley from 5/16" out to 3/8". basically a newer 2003 block can be used in a 1996 Cobra since the early Teksid blocks are harder to find. in fact, Ford discontinued the service short block for the 1996-98 Cobras due to the expense of the Teksid Italian block. the 1999/01 Cobra short block can be used as a replacement by drilling out the knock sensor holes as described above.