The Source 4WRD retrofit will fit on most Source Four Fixture bodies. An exception to this is all Source Four bodies produced during 2015. This is due to a temporary change that was made to the metal on these bodies.
If you have a 2015 fixture body and are looking to install a Source 4WRD retrofit kit onto it, please give ETC a call so that we can get you the proper parts to make it fit.
How do you determine if you have a 2015 fixture? We mark the yokes of all fixtures sold with a sticker denoting the month and year in which the fixture was produced:
The fixture in this image is from April of 2004.