John's Gingery would seem to be as close as you get in practice to the original Gingery design.
Harvey's furnace is a slightly scaled up but otherwise very Gingery furnace, except for the burner which is almost identical to my Mark III:
Tom's Variation has possibly a sligthly easier to build lif mechanism. Based on a geared winch I would think it is a litle slower to operate which could be a problem when casting iron. The telescopic column system may be liable to stick-slip, unless it is rather loose. Combine this with the almost-on-balance support of the lifting body and I expect the operation is less than smooth.
Scot's Neat design has a lift mechanism not unlike the previous one. A neat package though the gas tank is a litle too close to the furnace for my liking. Both this and previous design support the weight of the furnace body with a cable which would worry me. As Scot reports a broken wire lead to a cable failure during construction...how would the cables take a spill of liquid iron?
Loren's Incomplete is a no frills design and the lift mechanism is not displayed.