5K's must be a fair bit lighter than 4k's for whatever reason. I bought a 5K with attached K50 last night and had no way to get them off the back of the ute other than my own two arms and back. So I pulled the gearbox off the motor whilst still in the back of the ute and lifted it out. The gearbox has bugger all weight in it so I'd say 25kg's would be a good guestimate.
I was then going to seperate the head, block and manifolds etc to lighten things up so I could then heft out the rest but decided I couldn't be bothered as it was nearly 9:30PM and starting to rain again(plus apparently the sump is still full of oil...a disaster waiting to happen). As the alternator has been located on the other side to the manifolds on this engine(the 5K in Rosie, my KE30, has them all on the same side) I used them as handles and lifted the motor out. It wasn't too much trouble so I'd guess it weighing in around 100kg's? Might have been easier as I could keep the load nice and close to my body and it was distributed pretty evenly.