@GorillaTactics2089, I'll cut right to it. If you run an A5 extension or the Armalite AR-10 Carbine Reciever extension, or the MagPul SR-25/M110 extension - those are all 7 5/8" internal depth, and they are the original design for the AR-10. You must run a buffer that's 3.250" long. The buffer you first listed is a great buffer, but it's 2.500" long, made for a Large Frame running an AR-15 Carbine Receiver extension, which is 7.000" internal depth. True design depth is 6 15/16" internal depth. Every small frame out there does just great with 7.000" internal, though.
So, the buffer you listed is too short to run with the extension you've chosen. The extension you've chosen is the proper depth needed to balance the recoil system to the gas system, on a Large Frame. If you order this buffer from Slash, if comes with an Armalite EA-1095 recoil spring... This is all you need to finish your recoil system...
https://heavybuffers.com/xhcar.html