Try the many on-line auto parts sources for the replacement parts, such as; www.RockAuto.com, or www.autopartswarehouse.com, or www.discountsteering.com.
Be sure to first check the overall condition of the steering system from the steering wheel through the linkage all the way to the tie rod ends. Make sure the steering linkage is rebuilt / solid condition (little to no play or looseness) before addressing the steering gearbox to obtain a tighter 'feel'.
Also, recognize the older design worm and sector or recirculating ball configuration is simply not as responsive as the modern rack and pinion - by virtue of design, development and advances in materials though the years.
There are many parts resources for the steering gearbox; for not only rebuilding but also for exchange for a quicker-ratio unit. If I remember correctly, the quicker ratio steering gearboxes had a part number ending in -AX suffix such as for the Sprint or GT models.
Anyway, some of these parts sources are; Dearborn Classics, Macs Antique Auto, National Parts Depot (NPD), and Borgenson. In some cases - the existing steering gearbox can be rebuilt using the upgraded components for the quicker ratio steering inside the stock-appearing OEM gearbox housing.