Can anyone help me out with this? I've got the engine ('93 TBI 350 4L60e (from a G1500, all stock) installed in my 67 EC and enough of the wiring, fuel pump and lines to get it to fire and sorta drive. At this point the trans won't shift. I think what I'm missing is the VSS BUFFER. The connector where the VSSB should be (I believe) consists of a large red wire, the two shielded wires from the speedo sender, and a blue wire to the PCM. At least I think what I need is a VSS buffer, although in one thread from diy-efi I have seen mention of a DRAC working in conjunction with the VSSB. Any insight would be greatly appreciated.

You're right, won't shift without the speed signal. And you do need the buffer, (built in to the DRAC,) buffer converts the sine-wave signal from the VSS to a square-wave signal for the ECM. Or, the easiest thing to do would be to get a 4PT signal conditioner from Jags That Run (http://jagsthatrun.com), the are about $80.00.
You can also download the chapter about speed signals Here. (http://www.jagsthatrun.com/V8-chapters/V8-tpi-Speed-Sensors.pdf) from their book, TBI & TPI Engine Swapping....good book by the way, worth every penny.