Shmoo,
Unless you are really interested in converting your front-end (steering and brakes), I agree with Ghostrider and hotshoe36: (1) is your steering box really NOS; and, have you tried to adjust your steering box and steering linkages (if they are adjustable)?
A tight original front-end can feel smooth and safe, even at "highway speeds" (55-65 mph, if you have a 3.90 or 3.55 rear-end).
If you cannot tighten up the front-end, then converting or repairing are your choices. If you cannot do the front-end repairs, you are at the mercy of the knowledge, experience, and skills of your mechanic. A mechanic who has never worked on vintage front end will of course steer you (sorry for the pun) towards modernization.
If you choose to modernize your front-end, and you will not be doing the work yourself, make sure you are paying someone who has done this type of job at least a few times.
Tim
