63-72 a-arms shafts are a much better/more durable design than the softer 73-87 rubber bushings that degrade and deflect, and I'd bet they'll also outlast aftermarket urethane/delrin bushings found on tubular arms. The original cross shafts/bushings looked brand new with no wear at 150k on my truck. New shafts are dirt cheap on rockauto and come with new seals.
I'd stick with the stock arms, do the caster mod on the lower control arm shaft (thats the only benefit those tubular arms usually offer-added caster), and use CPP's 63-70 disc brake kit. 1.50" bolt on spacers will clear the studs and calipers with stock drum brake wheels. It'll drive really well with those mods and track dead straight at interstate speeds. Steering effort will be pretty high in parking lots with added caster and added scrub radius from skinny wheels with spacers but if my skinny arms can deal with it I'm sure yours can deal with it until you get power steering
That's the recipe I used on my '66 and it drives great other than heavy steering in parking lots. Spend the money you save on tubular arms on power steering instead. I have a Borgeson box waiting to go on mine when I get some spare time.
