For the rolling stand I made mine close in height to the tailgate of my truck to facilitate loading.
The K27 in 3/4 will be slighty larger and heavier than my A3 in 1.5. My guess is that you will be able to lift it until you have the saddle/cylinders/smokebox attached, at which time it will probably stay on the stand for further work. I found that when doing things like aligning the crosshead guides it was useful to be able to set the frame onto a surface plate, so I used my normal workbench until it got too heavy to lift.
That said, I did use a cherry picket and my auto lift a couple of times to move it to the floor of the shop and back up.
