Transfer box output seal assembly

my transfer box was leaking into handbrake drum, I believe the cause to be a groove in the flange.
hard to describe but the old flange was of one diameter along its length, the new one has a chunkier bit at the base of about 5mm depth. the old one had a mud seal that fitted over the gearbox casing, this one appears to fit inside it. I have tried taping it over the flange so it's flush as suggested on a forum but it is very tight and doesn't seem to want to go. which way up should it be fitted?

any suggestions? any reason that I can't just use the old mud Shield with this flange?

Fit a speedi sleeve to the old flange

Mismatching mud Shield and flange?
Flange on the diff can also have the same problem and also the seal also depends on which mud shield you use.

If your old shield fits the new flange firmly then that is the answer.

Post deleted! Wrong transfer box!

problem solved, old mud Shield fits over the casing, new one fits onto the flange and sits just inside.