The only difference between the "new" Lever body and this, is the appearance.
The new lever blade (be carfeul, NOT the race/trial zone lever) will fit without problem. And without loosing power. Of course, the new lever is shorter, but also the axle-force point is. So you still having the same braking power. Attention at the nut. If you have the old one (not gold-colored) you'll have to make it thinner or it wont slide correctly in the body when you pull the lever