The endless pool will certainly help if you can get over there. I know a few people
who have one, and they train nearly 100% in them. If you can't get over there often, you could try getting some stretch bands and do some bent over rows like in the video below (at ~6:40). If you are confident in your swimming, the main thing is to make sure your muscles are trained. I've done 2 70.3s without doing any swimming leading up to the race, and the only problem was my lats cramped a bit near the end.
It also sounds like Lubbock 70.3 will happen in late June, and Mike Reilly already announced he will be there to announce. I'm tempted to take a road trip.