I'd have to agree with the others, if'n you're wanting to do an original resto then your guidelines are cut and dry but if it's a resurrection then it's all personal preference.. and as they say "beauty's in the eye of the beholder."
Greg Fall's '50 works great with the yellow... I think blackwall's would've been too harsh a contrast. And Brian.. I think your '56 looks awesome with the ww... it works especially well because your bumpers and grille are white so it carries thru. Nice ride!