Just an update on my conversion, after advice from Robert Holler, I was able to put the S40 front fork on my V20. The S20 fork steer tube is longer than the V20 so you will need some extra shims. I happened to have a steer tube extender on the V20, which I removed but used the shims for the longer steer tube on the S40 fork. Now I no longer need the extender.
The S40 26 inch wheels now fit on the V40 with 2 inch tires (Schwalbe Marathon Mondial). The back is a real close fit, but works. The front is good with the new fork. I had trouble with the back brake rotor. It was rubbing on a weld point at the dropouts. I used my Dremel to grind down the weld and now it works. Robert said the old V20s had this issue. It's fixed with the new ones.
The SRAM Rival hydrolic brakes come with connectors and filled with brake fluid. But, if you want to run the back brake line through the bike body, as I did, you have to cut off one of the connectors to fit the tube through the holes in the frame. But that's not all, the standard brake hose is too short, so you have to purchase a 3 meter hose and replace the one that came with the brake. Now, after running the hose through the bike frame, you have to add connectors to each side of the hose and connect them to the brake and shifter.
I had to use a bunch of washers to make the SRAM Rival front brakes fit the mounts that I already had for my previous brakes. I have a IS to post mount converter. Then I used a post mount to flat mount converter for the new brake. I couldn't find a spacer on line to make the brake work with 203 rotors, hence the washers. I'll keep looking.
On the back brake, there's an IS to PM converter and a PM to FM converter, which worked great with my 180 rotor.
After mounting the brakes and seeing that they don't rub on anything when spinning the wheels, I had to bleed the back brake, since I replaced the hose. That turns out to be a two person job and not very much fun. I long for my cable actuated TRP HYRD brakes as they are sooooo easy to install and they work so well. Once the bleeding procedure was complete, I went to look for the bleed screws, and one was missing. After tearing up the whole house several times, I gave up and looked for screws online. I found some but I can't get them until Wednesday (4 days). I ordered them and then the next day went to 3 different bike shops to see if they had any. Nope. So, now I wait and get fatter.