Using 140.6 Training program for 70.3 race

The half and the full are different races.  Yea, you can train using the full plan as you propose.  

I assume the time commitment to train using the full plan is acceptable?

I assume your half performance goals are modest enough to achieve using the full plan?  

If you're really trying to rock the half, you can devote the training time of the full plan but tailor the workouts to optimize performance over the half distance.  

You could probably halve the long ride and long run, but you probably don't want to halve most of the other workouts.  

Volume and intensity will be different.  I'd want 3-4 60ish mile rides at or above HIM intensity during the build phase...maybe topping out at 100-110 miles for 3-4 rides over the course of a week.  20-30 miles per week running with a few long runs of 12-14 miles during the build.  8000-12000 yards/week swimming with race specific intervals closer to your race date (ie. 5x400, 4x500, 10x200 - all on short rest).  I know people say it's all about the bike but if you don't have very good swim fitness you won't be able to hit your bike and run numbers.

Matt Fitzgerald's Super Simple 70.3 plan might be worth comparing to your plan... I tended to swim and bike more than he had laid out in the plan...probably should have run more too since I started hurting at mile 8 both times I raced Chattanooga 70.3.

http://www.triathlete.com/2010/09/training/super-simple-ironman-70-3-triathlon-training-plan_12364

No...cutting things down doesn't make sense.  I always seem to race best at shorter distances when I am trained for longer races. For example you don't see many canned 10k running plans that have you do 16-17 mile runs, but I do them because I got used to doing them when I was training for marathons and when I drop them I am not as fast in 10K's or HM's (or even 5K's for that matter).