I used 6" vinyl numbers I bought from a sign shop on line. They are pre-aligned. Just peel off the wax paper, smooth them in place on the skin, and peel off the backing paper. Great thing is that car wash will not dislodge them as sometimes happens with decals. They can be removed with a hair dryer.
I ordered 96329632 and cut them in half. That is cheaper than 2 separate numbers.
John W. Irwin
2005 Classic 28 "Sabre-Dog III"
2013 Silverado 2500HD Duramax/Allison LTZ
WBCCI #9632, TAC TX-10