I'm puzzled as to why the noise has returned after replacing the front prop.
You said it disappeared when you removed the front prop and ran in 2wd - yes?
Then you replaced the front prop with a cardon type and the noise returned - yes?
I'd have thought that, if there was a problem with the rear prop, the noise would still have been there when you were running with the front prop off.
Is the replacement front prop new or second hand?
Is the noise exactly the same as before, or has replacing the front prop reduced it?
Have a close look at all propshaft UJs - can you see "shiny" patches on the yoke edge where it has been binding?
Another possibility is that you have a problem with the front diff input bearing. If that were worn, it would cause the noise when under load, but when the propshaft was removed, it wouldn't have been under load.