Question on maximum card available with specs below?

[Oldie]

Background - I have access to lots of old desktop PC's, and the space/power to run them at 0 cost (no OS cost they come with Win7).  They each have a slot for a PCIx16 card.  The power supply is 320w, and I can supply a single 6-pin power connector for a card.  It cannot be a full-size card, it won't fit in the case.  So, question is what is the best (available) card I can put in the system to setup a mining farm?

I was looking at the 6770's, have one on order and should be able to try it Monday.  Can anyone suggest a better one?

Thanks

[Protagonus]

As long as it will fit in your cases, which I believe so;  Maybe the HD7850's  They should net you about 100-150 higher xH/s (not specifying L or B,  so X) and only with 30w more power appx. So, still plenty for the 350w supply and only a single 6 pin for power.

[Oldie]

I looked at those but I don't think they will fit.  anything 8" or longer is too long.  Also looked at the 7790, and ordered one of those too, it looks to fit the case.  We'll see.

[Protagonus]

O.o 8".  Okay it will fit; well certain MFG's.

PowerColor Radeon HD 7850 2GB AX7850 2GBD5-2DH   8"
Club3D Radeon HD 7850 CGAX-7856   7.79"
MSI R7850 Twin Frozr 2GD5/OC  7.76"
XFX Radeon HD 7850 1GB FX-785A-ZNFC 7.75"

May be others, but those definitely will work for ya then.