Same spring they use on there Wedge head. 1.55 single spring and damper, about .550-.590 max lift.
Nothing special thats for sure, any kind of perfomrance upgrade over stock stuff will get these changed out.
I have lots of info and flow numbers for these too.

[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]