Can't migrate files "don't have permission to read" - how can I reset access?

Question

Hi,
I bought a mac mini, the mid 2010 model, it had Snow Leopard. I also have a PowerPC G5 running Leopard. So I migrated my files to the mac mini. Then a week later the new mac mini came out (last week). So, preparing to swap my new old mini for the new new mini I copied all my files BACK to the PowerPC. Got the new new mac mini, and of course it runs Lion. I tried to migrate my files but Lion and Leopard (not Snow Leopard, and it can't be upgraded because it's a PowerPC keep in mind) don't play well with each other. Fine. So I next tried to straight copy the files over my network. No go because I get this message:
Items can’t be copied to “Desktop” because you don’t have permission to read them.
I'm using the same login and password on both computers. Both are administrator level. The permissions for the systems themselves have been repaired. I've also tried to set the permissions to the files I want to migrate using this terminal command:
sudo chown -R yourusername:staff  (and then dragging the folders I want blessed into the window)
no go... says I don't have permission to do so.
I tried "pushing" the docs from the other old computer to the new. Doesn't work
I'm trying copying to the Public folder now - and while it works for MOST of the documents many are still being left behind with the same permissions problem.
So, here's my question, given I've tried the above: How can you reset an entire folders contents to become absolutely "public"? There must be a way to do this that I'm missing. Again, I already realize I'm copying from different to new computers, but in Lion I can't seem to reset folder permissions to include "all subfolders" or "all files within this folder" (or whatever it used to say).
Thanks for any suggestions

Answer 1

Thanks for the help Pondini (gave you a "Helpful Answer" 'star' ). A couple of things, so others have it in front of them:
Setup Assistant can only be used at first install - otherwise you have to reinstall to use it.
Second, it's "dumb" that you can't use network between Leopard and Lion. ARGH. - especially since the firewire ports are different on many newer and older macs (and I mean older as in just over 4 years - not that old really). However you can get adapters (that's the next thing to try) that will change the old pin (4 pin I believe) to the newer (9 pin I believe, have to check that one).
The 501 reference I can check, thanks - I recall seeing that long ago in poking around
On the Lion machine it reads
User ID: 501
Group ID: staff
On the Leopard  machine I want to copy from TO the Lion machine it reads:
User ID: 501
Group ID: 501
So it seems possible (I'm not sure what I'm seeing - educate me please lol) that the Group ID's don't match, where the Lion machine is staff while the Leopard is '501' - does this matter?
Thanks.