Okay we know that a variety of coil springs are probably not actually made by OEM's. They probably sub out specs for them slap their part number sticker on them and jack up the price by 50% or more and call it their own.

I have been looking and cross referencing numbers but the question is who supplies these to OEM's and will they sell direct to end user or aftermarket places or are they prohibited from doing that by licensing agreements ?

JD and I am sure others as well happen to use the same coil spring for multiple uses. For example the 1610 chisel plow spring is the same part number as the down pressure spring on a 750 drill and a multitude of other JD implements.

Surely these can be had in the aftermarket someplace or can they be searched for in some other manner or cross referenced to a different brand or secondary equipment maker ?

Has anyone else had good luck sourcing coil springs outside the normal distribution channels if you know all the measurements, material and compression factors and number of coils ? 

Heavy duty coil over shocks place perhaps where you could specify spring parameters ?