Based on the 3 options, no doubt I'd go t56. It is the most work also though as mentioned, takes some cutting. I wouldn't mind having one of Passons 5 speeds for my belvedere, but I lack the patience to wait for one.
There's a thread with lots of pics on FABO by a guy who just did it. "Some cutting" is an understatement
It came out great in the end, but he also included a price list. Cost about $6000 AND he did a huge amount of surgery.
Meanwhile, although it may take a long time to get one, the Passon A855 is $5500 and bolts right in
