Hm, for 4x5 and 5x7 Speed I use Velbon Sherpa 630 with PH-250B head.
For 5x7 Ansco and 8x10 I use some old Soviet aluminium videocamera tripod with low-profile Gitzo P.L.5 (?) head. A bit heavy contraption but works great, the only drawback being a bit too high minimum height.