It's a good garage project, but it looks to me like exactly that. There are plenty of folks here on this forum who can do work that good and far better. I know a dozen welder/fabricator/machinists who could do that work, most of whom would not have the experienced eye or taste to make the parts look more like Stevens parts. 

I don't see anything there that couldn't be pulled off in a reasonably well equipped home woodshop. It'd be a lot of work to do it that way, but a lot of work rarely gets in the way of an inspired hobby gunsmith who has probably been reading too much De Haas.

The rifle has a 7:00 extractor, near as I can tell.  (Why do these cell phone camera pictures distort so much when put up on websites?) That would indeed indicate that the original frame was in the “low” serial number range, i e, six figures.)

Looks like the builder also rounded off the octagon flats on top of the receiver.  It does look now like the hammer and trigger (as well as the lever) are shop-made.  Is the barrel now threaded into the receiver?  It seems the takedown screw was done away with entirely.

There is nothing on that rifle that is not within the skill level of the ordinary home shop machinist, if he is careful and takes his time.  Those whose idea of a “rifle build” is sending a spec sheet and a check to a gunsmith and calling every week for a progress report might get one of these kid rifle actions or junkers and see what they can do with it themselves.  The ordeal experience can be quite instructive and is very interesting.

Why would someone take the time & trouble to re design a Favorite action, I can see no improvement.  Ledball