Chris,
I ran a 51 for a while and while it make big power, I found it a little lazy trying to spool it up with the stock D5. Lots of negatives on the 51 reliability but mine worked perfectly and looked new the day I sold it.
The sweetest turbo/converter combo I have ever run for street, track and low-buck was a TE-60 with a .63 Garrett and a 2800 restalled D5.