[Mr70]

"What would be the correct clutch for a 1970 Camaro SS-L78 and would the date be prior to the engine build or the car. The engine in my L78 was built over 6 months before the car."

I would use the Cars overall cowl tag build date as the reference point,not the engine Tona date.
Yours used Fan Clutch Part#3946050,same as the 1969 L-78 Camaro and Fan Blade #3947772.

budnate
I gave you misinformation earlier.
You should have Fan Blade #3789562 18" diameter 5 blades 4 bolt circle.
Sorry.