The Texas Special used E-7s. Later, two ALco PAs were added due to the popularity of the train. Not sure how long those lasted. No F units of any kind were used on the real train. During their existence, Lionel (and other manufacturers as well) have frequently used non-prototypical engines as "stand-ins," for various reasons. Some have tipped more in the "fantasy" direction than others. Welcome to the world of O gauge! In the Post War era, they didn't make any E unit diesels; in fact, none were manufactured until fairly recently. Lionel did do a scale Texas Special with E-7s and 21 in. cars several years ago. However, scale E units with scale length cars make for an enormous train, useable only by those with very large layouts.
The Lionel Post War Celebration series Texas Special used F-3s, the same as the Post War version it was replicating, and 15" aluminum passenger cars. The Neil Young Texas Special set of just a few years ago did as well. These sets are very nice - really like my NY set. They're great for persons who don't have huge layouts, which is most of us. The shorter F-3 engines still make nice replicas of the originals. Some imagination may be necessary, but very little, for those who are short of it. (Of course, other than trainheads, 99% of people observing the sets aren't going to have a clue about the difference between F-3s and E-7s, let alone what line used what engine for what.) The NY set with the F-3s and 15" cars are not only very nice replicas of the original, but more useful on a far larger number of layouts. I think the FT LC+ set will be a great set for a lot of users as well.
