AR- 850-5 pg 46 has the Army's regulations for Halftrack markings - also has the exact dimensions for the numbers letters, etc on page 49-52
http://jeepdraw.com/images/AR-850-5.pdfI have used Rick Larsen stencils for a M416 build I did - Absolutely first class.
If you are going to do a 2nd Armored or 3rd Armored Division remember they retained the "Heavy" 1942-3 TOE structure - 3 complete Regiments which each had three battalions, while 1st, 4th -14th, 16th and 20th Armored Division went to the Light TOE (Combat Command A,B and R) So a 2nd Armored Division Halftrack from 2nd Battalion HQ section , 66th Armored Regt would have the bumper numbers 2^66^ (pass side) 2 HQ-7 (driver side) The 2 before the HQ indicates 2nd BN. Regimental HQ vehicles including the RECON Co. would have no number before the HQ.
Speed numbers in Yellow (tactical numbers) were also used in the early stage of the ETO but seemed to phase out by Operation COBRA when the units started applying flat black camo.
Can anyone make out what the shipping markings are on the M2 from the 41st Infantry HT ?