[William]

Chevrolet service info strongly warns against mixing conventional parts with variable ratio.

“The pump used on vehicles with variable ratio power steering provides increased fluid flow at higher pressure than the conventional pump. Consequently, the conventional pump and the pump used with the variable ratio system are not interchangeable. A new pump outlet hose is required on variable ratio power steering equipped cars.”

-1969 New Product Training Program Booklet

“Internally, the only physical difference between the variable ratio system and a conventional system is the rack and sector gears. However, higher power steering pump pressures are required so it was necessary to strengthen the steering linkage accordingly. The relay rod is now a larger diameter, and constructed of higher strength steel. The same is true for the pitman arm. Because of the substantially higher loads imposed on the steering linkage, variable ratio steering gears should not be installed on any past model cars.”

-1969 Product Review