Way back in 1997-2004 when I had my 1971 Plymouth Valiant all tuned up, first with a BBD and later with a Holley 450 mechanical secondary, I also had Clifford Street Rod headers on the car. My solution for the kickdown linkage was using the stock Super Six linkage and mounting brackets. After some careful measuring, since I no longer had the stock exhaust manifold on the car, I used longer bolts with tubular spacers, so the linkage mounting bracket was in about the same position. It worked for years.
Either by using a kickdown cable or some other way, I'm sure I can engineer a solution if I can't find factory parts.
Maybe someone has enough parts laying around to measure and compare Super Six and non Super Six transmission kickdown levers? I always adjusted mine to have full kickdown lever push-age at wide open throttle or just before.
In the winter, I'd use flexible 4" aluminum dryer duct hose clamped onto 2 header tubes and routed into the air cleaner inlet, with a hole poked in the dryer ducting, to provide heated intake air.