I'm going through a bunch right now...
I already run an FD alternator on my FC 13BT.
I've got a "160A" FD unit off of eBay for like ~$160.
It's a disappointment.
The damn thing barely idles @ ~13.0VDC.
Loaded down at idle, it runs about 12.0VDC.
The seller was named "HighAmpSpecialist" or something like that.
One of my previous posts talks about having good experience (rebuilt starter for my FC) from an eBay seller "AceAlternators" (or something like that), but they don't offer an FD unit anything over 130A now...
They used to have a 160A, but I haven't seen that unit for sale for a few months now.
There's another eBay seller called B&R or something, and they offer FD alternators in the 160A range for about $200?
Check the feedback. and there's negative comments of the upgrade alternators being bullsh*t.
I would highly recommend to go with a MechMan unit if you got the bucks...
Last time I checked, it was about $330?
Yes, it's a little pricey, but these things are rated like 250A...
http://www.mechman.com/
-Ted