Within this page, you can find a complete list of all 4-letter words that end in AD.
That list comprises a grand total of 33 words. On average, these words are worth 6.7 in Scrabble. However, the best word you can find on this list (or at least the one worth the most points) is QUAD, which is worth 14.
Using the WordsRated word finder, you can also find a list of all 4 letter words or, given that we have already established that you have AD, you can also check out the words ending in AD.