If you are interested in the real Mi-Jack specs I am posting them below. This will get you all the way to true scale. These specs come from the 1997 edition of the Car & Locomotive Cyclopedia. There appears to be at least four different specs for this model so I will give the smallest.
MJ1000R Translift
Overall height of machine 37'11"
Overall width of machine 47'6"
Inside clearance 38'6"
Wheel base 20'0"
Length to outside wheel guards 28'8"
Ground to side beam 8'8"
Height to twistlocks 22'6"
Happy building!!