1969 Race Dart w/ 426 Hemi- garaged for 45+ years

for Pro-Stock
early 70's...state of the art was ladder bars and leaf springs.
for a short period (71-72) there was the leaf-link. leaf spring on the bottom (to locate and hold the car up) with 4-bar link on the top.
by 74....it was all 4-links

that's how I remember it.
View attachment 1716136692.

the suspension pictured is the 1975 Direct Connection Duster Butch Leal raced in NHRA modified production (M/P). The rules required OEM front and rear suspension (leaf springs) and allowed traction / ladder bars.
the leaf link you mention is called an anti tramp bar setup in the uk. as you say the front half of the leaf spring effectively becomes the lower 'link' of a 4 link. they even came as factory equipment on some mid to late 60's fords here.
neil.