I really screwed this one up. Careless in keeping my valve body springs with there proper pistons, I managed to get them mixed up.
I found an explanation online of the spring numbers per the ATSG manual and have found a home for all except one, the EPC spring.
The spring that I think goes on the end of the valve measures 6mm X 23mm and it has a very soft spring rate. The ATSG manual diagram tags it as #320.
It fits perfect on the nub at the end of the piston. The diagram I found calls out for an 8mm X 23mm spring. I don't have a spring that size nor do I think it will fit in the bore.
Can anyone tell me what size spring actually goes on the end of the EPC solinoid piston?

Here is a valve body breakdown.

http://www.atra.com/bulletins/2009/july/atb1264.pdf

The spring I am referring to is the torque signal regulator valve spring.

The pressure regulator valve spring inner nearly the same size except the diameters are about a millimeter different

Wow this is a tough one, I know you want to get it right because the side cover isn't a fun thing to take off in the car. My suggestion is to go the the wrecking yard and see if they have a 4t65e core they would be willing to let you rob the VB out of so you could do a side by side comparison. I would say go to your local transmission shop and ask for advice but in my experience they get kind of pissy because they missed out on robbing you of 1600bucks to rebuild it.

A have talked to a local shop on the phone about sizing the teflon seals on the input shaft and they were really helpful. I may just hit them up again or buy a used ebay valve body just to see what spring is in there.