Ok, so I had a couple things wrong in my original post. I used 1" ACME thread, not 3/4", and I used 1/2" plates for load dispersion. Here's a generalized cut list, along with a screenshot of a simple Sketchup drawing.
Bases:
2 - 2.5"X2.5"X3/16" square tubing, 24" long (you could easily go a little longer)
2 - 2.5"X2.5"X3/16" square tubing, 6" long (these must be 3/16" wall, to allow 2" tubing to fit inside without excessive play)
2 - 1" schedule 40 pipe, 19" long (I'd probably drop this down to 18")
1 - 2"X2"X1/4" square tubing, 44" long (I'd probably add two inches to this one)
6 - 3/16" or 1/4" sheet, cut to triangles for gussets (I used 10GA, but wish I'd gone a little thicker)
2 - 1/2" plate steel, 6"X10"
Misc things: I welded "stoppers" on the load plates to create a little bit of a saddle for the ACME rods, they are very necessary IMHO. I also drilled holes and welded two 1/2" NC nuts to the 6" tubings to clamp the two frames together. Obviously need bolts to match. I welded a 1" fender washer to the top of the pipe, where the ACME T-handle nut sits, to give it a good surface to ride. The ACME rod and t-handles I got from mcmaster.com. I got a 3' piece, and cut it in half. I haven't yet, but I will be beveling the top of the ACME rods, for two reasons: fit the saddles better, and it should also help keep the rod from trying to turn when I crank the t-handles. I didn't want to weld the load plates to the ACME rod, in case I ever want to lift a different boat.