I did just that, I bought a new back from the LF forum (as in my previous post in this thread) I think $50 is a real bargain. I'm making a camera to shoot 5"x4" and 6x17cm, maximum FL will be 203mm (maybe 210mm at times), minimum 65mm, and I'm using a Pacemaker Graphinc focus track and a Speed Graphic front standard to get more movements. The plan is a hand holdable light weight LF camera, with movements, I already have a WA modified pre-Anniversary Speed Graphic, built that way from new, and I just need a slightly wider body to allow a 6x17 back.
Should just add that contrary to whay's written elsewhere the 5x4 Speed & Crown and Super Graphic rails are standard but the heights of the rails above the trackbed aren't. With some modification a Super graphic front standard fits any of these rails.