How does one get the barrel off of a 1907 Winchester 351 sl, I figure you may
Know a gunsmith old enough or maybe someone at Winchester that may be able to find out.

https://www.bevfitchett.us/firearms-assembly/winchester-model-mvi.html

Let me see what I can find out.

I used to know a couple guys from Winchester that could help you. Unfortunately they passed a long time ago.

You might also try this website: http://stevespages.com/page7b.htm

Will also be trying to locate one of the retired gunsmiths I know.

Partsman , I have gone down that hole. Best answer is don't do it! I have gunsmith books covering it back to when it was issued and All state, " disassembly of this weapon must be done by the factory" .
As I found out that statement was correct. I did manage after weeks of study and making special tools to get mine back together . Don't remember how right off the top of my head but it is not something I would ever try again. Just my 2 cents.

Oh I have no issue taking them apart, got the reassembly thing figured out with a tool I made, but my deal is the latest one I picked up the guide rod would not come out , just spun and I finally clamped it to a rill with an adaptor and while the drill spun it I pulled on it an it finally came free, so I think as the threads in the piece which is part of the barrel are hooped, so I may have to pout my new barrel on it.

think you have it figured out, instead of putting a new barrel on it , unless its needed, insert the guide rod in the block drill through the block into the rod , thread and install a allen screw.
I had one that was repaired by the factory,(according to the paper work I got with it) in that manner. I really couldn't believe Winchester would do that but the papers were there!
most common failure besides the forearm cracking like a brittle ice cream cone, was the firing pin. next seemed to be the actuator rod threads in that block.

The foreend has a worse crack than they said, bore is pitted, but there is some build up of what look like flakes, I tried some wipeout and patches were very blue.
I think the firing pin must be broken in two, as I push it and the back half springs back, but you can see it sticking out the front and it can be pushed back.
They offered to buy it back but I told them I like tinkering, so will see how it goes and I will have to try that repair, I had thought of just running a pin through it.

so heard that you can unscrew the barrel, but would need a barrel wrench, and somehow you have to hold the receiver without crushing it, any ideas where to get tools like that
or pictures of what they would look like

Try Numrich Arms. They might be able to help out. They carry some oddball stuff, parts and occ, I have seen tools listed.
I spoke with them at SHOT Show this year, they said they will ship
to us here in Canada.

I think the next question is how to reassemble a Nylon 66.

Step 1: Find all the flying springs.

Step 2: Buy a replacement Nylon 66