Centering MII Frontend

[whitedog76]

Ok, I received my MII crossmember the other day. Now the hard part starts.

Most all of the MII kits out there state to install the crossmember 18 1/8" centered from shackle mount.

The factory assembly manual states 18.28" (let's call it 18 1/4).

When dropping a string line, I'm at 18" to center on my solid axle. Of course, that's with 60+ year old leaf springs. If you look at a picture of my truck. (It's not a good one, but the only one I have with the factory sheet metal in place.) The front axle is a little far forward in my opinion.

I'd like to run around 5 degrees of castor. The instructions on the top hat say to install it at 1 3/4 forward of the crossmember. So, my way of thinking is to install the crossmember at 18" and shift the hats back a little bit. From doing some math, there needs to be 3/4-1" difference in the centerline of the spindle in order to get my 5 degrees.

Am I on the right track or am I over thinking it?