In reading all of the suggestions here I am struck with one over-riding thought: We are ASSUMING that a terminal cross is the primary goal with this breeding plan, and I agree that is a reasonable goal. But, to resolve the seeming 'negatives' which are present in MOST Longhorn bloodlines concerning Terminal traits, In My Opinion, it will require more than two breeds in the mix, and certainly more than just the F1 generation to achieve the results you are seeking. Crossing Longhorn Genetics ( such as Ryan has in his cattle!!) containing Muscling, Substance and Carcass traits - and THEN crossing them with Terminal breeds, as has been mentioned here before, will give you a FOUNDATION F1 female to which you can cross with ANOTHER breed ( 3rd breed ) for real Crossbreeding Heterosis. A breed such as Gelbvieh, or Polled Hereford, or Angus, or Red Angus, or Piedmontiese, or Chars, or any of several which have been mentioned here would work very well - CONSIDERING the fact that retaining the VERY BEST individuals for mating is as important as the Breed!
BUT - NOW we are talking about a long time for the ultimate results to be obtained - 9 - 11 years or so. But that is the cow business. It is not a "Get Rich Quick" operation! But, anything worthwhile takes time and thought, and "Beef Breeding" is certainly that!
Optimal seedstock choices are imperative for successes in cattle breeding. You just have to know what your goals are BEFORE you start mixing and matching!
DOC HARRIS