How much trouble will it be to rebuild the front end?!

I think I can answer this one for Redfish. The 67 K member only has one support for the idler arm whereas the 68 K member has two. To use the 68 idler you`d have to weld an upper support on to the K member. The modification could be cost effective because a 67 idler arm is way expensive (over 100 dollars) while the 68 idler is a fraction of the cost.