How can you get a good grip on the barrel and turn the receiver without dammage to the receiver extension for the mainspring and forearm? Are there special bushings or tools for this action?
Thanks...Jon.

No, you must completely disassemble the receiver and clamp the barrel as close to the spring as possible.
You MUST have a barrel vise and barrel wrench.
Also, remember, the Ruger #1 barrels have a taper to them so if you use regular un-tapered bushings you will probably have to use a good amount of Rosen.

-Spencer

I don't normally disassemble the entire receiver, it ain't necessary and I don't use a special action wrench. I have a lathe-bored aluminum bushing that is bored to the same taper as the barrel, dusted with rosin powder and tightened down in my barrel vise. The action wrench is a 15" Crescent adjustable jaw wrench with a heavy paper as a protector against scratches on the receiver. Works every tim, just make sure you have the lever open so you don't twist off the extractor and the rib/scope base is off.

Thanks...I've never worked on one of these before and was wondering if it would be ok to clamp the barrel so far from the receiver. I have a good barrel vise set up for Mausers and will cast bushing inserts for the #1 out of cerosafe.
The plan is to re-barrel to 7x57R but want to be able to re-install the (hopefully undamaged) 45/70 barrel someday.
Thanks again for the comment.

Jon