The answer to your question
What is the morphological analysis (Part of Speech) of headed in where are you headed?
is “It is the past participle.”
The following is taken and heavily reduced from A MODERN ENGLISH GRAMMAR ON HISTORICAL PRINCIPLES by OTTO JESPERSEN Part IV SYNTAX (Third Volume) Published 1931. This is out of copyright and can be downloaded from http://arrow.latrobe.edu.au:8080/vital/access/manager/Repository/latrobe:34325
3.1(1). In English, as in the other Gothonic languages (and in the Romanic languages), the perfect and pluperfect are formed by means of an auxiliary and the second participle. […] its original meaning is I have caught the fish = I have the fish as caught
3.1(2). With intransitive verbs, have, as an auxiliary, competes with be [but] English has never gone so far as some other languages in the use of be […] In English be as an auxiliary is used chiefly with verbs of movement, but there has long been a strong tendency to use have in these combinations, too.
3). In MnE have is used to a greater extent than in any of the cognate languages and may now be said to be the regular auxiliary with all verbs. […] As a secondary cause we may mention the falling together in sound of the weak forms of has and is: he's gone, has gone [e.g. I've gone, etc., I'm gone]
[…]G. L. Lannert, An Investigation into the Language of Robinson Crusoe (Uppsala 1910, p. 94 ff.) gives full lists of the use of the two auxiliaries with intransitive verbs; be is in R C "far commoner" than have, but (p. 101) "in hypothetical clauses, where the condition is rejected, the use of have is practically the rule, both in the subordinate and principal clause". E.g. “I have not paid sufficient attention.”
3.1(4). For Present English we may say that *he is come means 'he has come and is here', he is gone means 'he has gone and is away', the moon is risen = 'the moon has risen and is now in the sky', they are rested — 'they have rested completely and are now all right again'
But he has come and he is come are not to the same extent "retrospective presents" (this is how the perfect is defined 4.1); for the retrospective element is much weaker in he is come than in he has come, so that the element of present is preponderant. While, therefore, il est venu, e venuto, er ist gekommen, and the corresponding Scandinavian phrases m a y be called perfects and are parallel with il a battu, ha baltuto, er hat geschlagen, the same is not true of Present English (though it may have been true of earlier periods of the language): he is come is a pure present, much as he is here or he is present, and all these phrases contain the verb is combined as usual with a predicative.