Would a pre 64 model 70 action set up for the 220 swift work for a 358 Win project, or ar their various issues relating to the semi-rimmed Swift case that would make this conversion troublesome? How about the mag, follower, and mag lips, etc.?

TIA.

I don't think it would be any problem at all to convert, here's why. The Swift and the 358 used the same mag spring, follower, extractor, ejector and bolt stop extension. There was no difference that I'm aware of with the bolt face either. The only difference was the magazine box, but that shouldn't be a problem either. The Swift had a box with a 2 3/4" opening, the 358 had a 2 7/8" opening. So you might need to remove the front partition in the Swift box so you have room. Or you could buy a new box from Wisner's to fit it so you don't have to monkey with the Swift box. I am not a gunsmith but I know a little about 70s and this project seems like a piece of cake.

Here is Wisner's website. I think you will find which parts you need from looking at the list of parts. The Swift was kind of unique in a lot of ways, mostly because of the slant box for feeding the semi rimmed cartridges. The 257 Roberts and 308 series have more in common.

http://www.wisnersinc.com/

With that said if you decide to go through this conversion I would be interested in getting the swift parts you don't use need. I have a pre 64 that was made from a standard action and would like to get the proper swift setup.