Greetings,
I am currently in the process of converting my 87 (stock rear drum) over to C5 Disks. From what I have read on here,, I would need a 1LE combination valve for optimum performance.
I have also read about the "upgrade" you can perform on the stock valve (the stronger spring.)
my question is, do I need to purchase the 1LE valve, or can I modify my stock valve so that it is compatible?

 

You can fiddle with spring rate in your existing combination valve. The thread linked below will give you a fighting chance to make reasonable choices.
Real 1LE combinations valves are not very common. If you can find one then buy it and use it. The code stamped on the valve is also described in the link below.

https://www.thirdgen.org/forums/brak...ng-torque.html

 

thanks brother