I like shooting around 8 inches/200mm for head and shoulders or close-up portraits. I'm quite happy with my 8 inch Kodak Commercial Ektar from the 1950s, I use it for all kinds of photography including table top stuff, although I find it not wide enough for landscapes. I paid about $250 for it. It has flash sync so I can use it with a speedlight or my monolights.
My other main lens is a 135mm so the two of them are a nice combination that covers off a lot of stuff I want to do.
Another option, since you have a speed graphic, is to use a fast barrel lens. I just got an F2.9 8.5 inch Pentac lens to play around with, I bet it would be awesome on a Speed Graphic. Although definitely not lightweight, it's a tank!