Yup, agree with everything here so far.
With the offset bushings you want to follow the instructions you posted here, NOT the included instruction. The original instructions are based around using them as a repair deal, not maximizing positive caster for use with radial tires.
The SKOSH chart is a good starting point for an alignment for radial tires. Personally I think the positive caster settings in the SKOSH are a little conservative, you can add a couple degrees of positive caster to all their categories across the board. Especially if you have power steering. Positive caster improves the “steer ahead” action of the car, it makes things a lot more stable at speed. With wide tires up front it helps counteract the tendency of the wide tires to seek out ruts. But the more positive you make the caster the harder it gets to turn the wheel, so if you have manual steering you might want to be careful as it can make the steering pretty heavy.
With stock control arms and offset bushings though about the best you can do is about +3.5*’s anyway, depending on ride height and camber settings. With tubular arms most of the non-adjustables can get up to around +5*’s, the adjustable UCA’s can go more.
I managed to get +8*’s with a non adjustable set of tubular UCA’s with offset bushings installed, but there’s no reason to run that much. I had the SPC’s up to about +7*’s at one point and they weren’t maxed out. But I run them at +6.25*’s, with 275’s and 16:1 manual steering the steering effort really starts to go up after that.
