You came out ahead on that one. A 50-70 is a fairly rare find (at least in as nice as a condition as you describe).
Here is a suggestion if you want to fire your 50-70.
Contact the folks at Friendship Indiana in the HQ of the National Muzzleloading Rifle Assoc. Though not affiliated with the NMLRA, there is a black powder cartridge orgainization that uses the range at Friendship every month. They shoot the 500yrd berm, and they are experts at BP cartridge, particularly trapdoors.
Thanks. I had contacted Dixie Arms at the time and I do have a mold and 50 empty cases. I just haven't thought about it in some time. I checked and my friend fiveshooter said that the 50's are making a come-back and I should be able to find a set of dies for it.