At the risk of being called an old fart ................ 1971/72
First car was a PB on-road. Can't call it a 'kit' really, more a collection of bits and a full engineers' 'Blueprint' drawing.
Chassis was a bit of 4x2 allie channel which you had to cut/file to the drawing. Came with the plastic bits for steering, wheels etc.
Rear axle was a length of 1/4" steel bar and the drive was from the clutch via a toothbelt straight onto one of the rear wheels.
Half eleptical from 'Cart' springs and quarter eleptical rear springs which you had to cut from an ally sheet, form to radii specced on the drawing, drill though and bolt together. No shockers, damping was by friction - the tighter you clamped the leaves of the springs together the more 'damping' you had.
Still got it all, including the box in the attic somewhere - I'll have to try and dig it out sometime.
BB