landtank, my compliments, you have come up with the first caster correction solution that I would actually feel comfortable adding to my truck (christo's is fine but too big for my lift). although you'd be drilling out a lot of dowel it looks to me that it will work down to 2 degrees or even one degree. I'd much rather install these than throw in OME bushings, and if the drilling is feasible it is not markedly a bigger pita than pressing out the stock bushings, plus you get to retain stock bushings.
so for the 4 and 5 degree corrections am i right that the problem is going to be drilling with the drill point on the crack? if so, one suggestion is this. For those two corrections only, instead of adding a positioning dowel to your plate, drill positioning holes in your plate in the stock location and then c clamp a second plate from behind with positioning dowels the stock distance apart that are the thickness of the stock bracket and your new plate. They would then fit through flush from behind into your positioning holes and give you a solid drilling surface. Might be as big a pita as drilling on the crack, but the backing plate does not even have to be welded to the dowels as long as it clamps them in place. Not perfect as you lose the "infill" of the partially drilled dowel unless you can weld the dowels in place or use a very thin backing plate.
that brings up one other suggestion, which is that you add one or two additional locating holes in the plate if you can find a suitable location that is easily drilled . I can see a risk of these things pivoting into the stock hole locations under load. maybe the dowel remainders will prevent that, but if they are spot welded to your plates they may shear away from the plate under stress and then drop out .
