I've been looking to purchase a body lift for my '93 F150 with the inline 6, all the companys say the lift can be used on my year truck but excluding diesel and 6cyl, why is that?

 

The problem with the body lift and the six is that the lower radiator hose is very close to the smog pump/serpentine belt. When you put the lift on they may contact. I put the lift on my F150 when it had a 300 in it. Just look for a lower radiator hose that is the same shape, but just 3-4" longer. That is what I did. I don't know the part number, but it was a gates hose.