I guess the way to think about this is as follows:
The most important thing is getting the caster right. If it isn't, it won't drive properly or even safely. If you set caster at say 4 degrees, your pinion on a stock 40 axle will be nearly flat. That does make for a steep driveline angle. You can either live with the angle, or do a cut and turn, so that you can have your cake and eat it too, ie both proper caster and a good driveline angle.
I don't know how much it would really add to the cost of a spring over-Mark can comment on that. As I said previously, though, the argument to do it, is stronger than the argument not to.
One last wrinkle--FJ62 axles have a different relationship between the caster and the pinion angle than FJ60(or FJ40) axles. They are already partially rotated in stock form! So if you were doing a SOA, and using an FJ62 axle, it might be worth setting it up and looking at the driveline angles before doing the cut and turn.
My pinion points exactly at the t-case flange. I don't run a CV shaft, because it would not fit, due to the reverse gear buldge of the SM420.