I'm trying to replace the flush and fill valves on a toilet stamped "1958, Standard F4043701, F404320x." Couldn't find those numbers anywhere on the internet so I bought a Fluidmaster Universal Everything Kit K-400H-021. Following instructions didn't match what I was seeing so I'm here to double check my work. See pics below. Thanks much for helping out.

Pic 1: The orange seal comes from the kit, but looks WAY different than the old one (pic 2).
Pic 3: This is how I found the lock nut. It looks inverted from the instructions; the flange is on the outside - away from the tank. That flange sat directly on the old seal (pic 2). (I assume the modern plastic lock nut with the flange on the tank side is already familiar here).
Pic 4: For reference, where all of this sits.

One) Is the Universal Kit correct for this toilet?
Two) Suggestions for removing that lock nut?








Edited 3 times.

For the tank-bowl seal, use this one
[www.amresupply.com]
This seal is thinner and because the rubber is soft, it will compress more.

Use a chisel and hammer tangentially on the flanged nut to loosen it. That is if you do not have a pair of 16 in Channellocks to grab the nut.

The order in which the assembly is shown in the photo is not the way it is normally done. The flush valve-tank seal is inside the tank and the the flanged nut goes directly on to the tank china from underneath. The tank-bowl seal then fits below the nut.