Oh ~ oops DUH !.
Sorry , I'd imagine you could either buy a Hot Rod linkage from Lokar etc. or maybe cobble one up from junkyard parts if you could find a yard with 60's & 70's tin in it .
The kickdown linkage on my '69 C/10/s TH350 is cobby beyond belief to look at but apparently is stock GM , it hasa 4" or so threaded part on the rod where it attaches to the throttle linkage , makes for greater adjustments .
A friend in TEXAS is working this out right now on a " Franken Benz " ~ they swapped trannies from the entirely wrong year so nothing matches and they're making up this linkage from scratch , non Mechanics , just determined DIY'ers on the Ranch...
A cable will of course be less obtrusive and look better , might be easier too .