I did some research on this a few years ago when I developed an intermittent clicking feel in my steering. Although I thought it was coming from the universal it has never gotten any worse and is mostly not there. With this I think that the universal is not the problem as it would likely not be intermittent and only get worse. At the time I purchased a good used one from eBay but have never installed it as it appears to be a pig to do.
When doing the research I am quite sure that the shaft for the 4 and 4.6 engine are different. Also if I remember correctly the shaft for the 4.6 that I have is the same as the F150 truck except it does not have a boot over the lower joint as mine does.
The shaft I got is from a 2005 Explorer with a 4.6. They used the same shaft in the 2002 to 2005 model years with the 4.6
