Need assistance with a shopping list to convert '68 GTS to 73-76 center link

You need a large spline box SO FAR AS I KNOW

There are 4 components that must be compatible. You need the later center link, obviously, 73/ later idler arm, ad pitman arm, and then a large spline box to fit the pitman. Everything else will fit

Exception is on a 67 if you have the original K member with the oddball 67 only idler arm