[dsraven]

u joints don't know or care if they are matchy matchy to anything else but their running mate at the other end of the shaft they run on. so, long story short, as long as the other end of the shaft is at the equal but opposite angles that they are running at they cancel each other out. thats why I mentioned to use a plumb bob, mark the floor under the critical points mentioned, and then adjust things until the axle is perpendicular to the engine and trans. if that is done correctly then the offset angles will cancel each other out and then as the axle goes up and down it will be a matter of adjusting the down slope of the engine and trans and/or the pinion angle of the axle so those angles match as close as possible at ride height. this can be a little tricky depending on the suspension type as some suspension types allow some flex under hard loads which will change the pinion angle slightly. leaf springs can have what is known as spring wrap, control arms can have different upper lengths compared to lower lengths so as the axle moves up and down the pinion angle changes. but, if youre set up correct at ride height then vibration and noise from an unmatched u joint set will be at a minimum.
there are youtube videos showing how it all works, spring wrap, uneven length links etc. take a few moments to apprentice under the you tube school of knowledge. lol.