So, starting from where Denny left off, I weighed some things. Now, full disclosure, I just used a cheap digital bathroom scale. I weighed each item a couple of times and took a bit of an average, but really anything within a pound of these measurements wouldn't surprise me. I also used a 73-76 /6 K because thats what I had laying around, but I'd wager a V8 spool K is within a pound or so, only the engine mounts are different and not much really for total metal used.
OE manual steering box:..........................12.4 lbs
OE power steering box, large sector:......... 37.5 lbs
Federal pump/pulley/brackets V8:..............15.4 lbs
73-76 spool mount /6 K frame:..................34.0 lbs
Stock tie rods & ends:...............................4.6 lbs
Stock center link, pitman and idler:.............9.6 lbs
Stock LCA's w/tabs, bushings and pins:.......21.2 lbs
Stock UCA's with ball joints:.......................9.8 lbs
Stock strut rods 73-76 w/bushings:.............4.8 lbs
Just Suspension 1" torsion bars:................ 17.0 lbs
Bilstein RCD's x2:......................................6.2 lbs
So for the stock K, manual box, and steering linkage my numbers give 60.6 lbs, which is real darn close to Denny's 60.8 lbs for the same items. For the control arms (upper, lower and strut rods) I get 35.8 lbs, which is 2.4 lbs lighter than Denny's numbers. I was a little concerned about that until I saw the stiffening plates on Denny's LCA's in the picture. Makes perfect sense, those are close to a pound each, so pretty close again. For the grand stock total, manual steering, I get 119.6 lbs. That's pretty close to Denny's 118.4, and I used 1" torsion bars.
So, now some mathematical gymnastics.
73-76 spool K, OE manual box, steering linkage, UCA's, LCA's, upper ball joints, strut rods, 1" torsion bars and Bilstein RCD's: 119.6 lbs
Same set up but with OE power box, federal pump/brackets/pulley/hoses:...........................................................................160.1 lbs
Same but only with power box (to compare to power rack, which also needs a pump & junk):...............................................144.7 lbs
We also know that the Borgeson box is 15 lbs lighter than the stock power steering set up, at least according to Peter Bergman and I believe him. That would mean a Borgeson power steering box weighs ~22.5 lbs by itself. So,
Same stock everything, Borgeson power steering box, assume same weight for pump& brackets as federal:..............145.1 lbs
Same everything, just the borgeson box, no pump or accessories(to compare to power rack):.................................129.7 lbs
What does is all mean? Well, the HDK and goodies are 88.5 lbs with a manual rack. So.....
The HDK conversion with a manual rack is 31.1 lbs lighter than a stock manual steering set up by my numbers. It's 71.6 lbs lighter than a full on stock power steering set up, but that's comparing stock power steering to a manual rack. If you assume the power steering pump and brackets for the Borgeson weigh the same as the stock stuff (actually not a horrible assumption since it uses a saginaw pump) then the stock K, Borgeson power steering set up to HDK manual rack is a 56.6 lb difference. But again, that's comparing power steering to a manual rack.
The problem is, I don't know what a manual or power rack weighs by itself. So, I can't make the power box to power rack comparison without assuming a power rack weighs the same as a manual rack, plus the pump/pulley/bracket/lines. Not sure if that's a good assumption.
If it is, than an HDK with a power rack is roughly 56.2 lbs lighter than a the stock K and power steering box, and only about 41.1 lbs lighter than a stock K and borgeson set up.
So you can only lose more than 50 lbs if you have stock power steering or a power borgeson set up and convert to a manual rack. If you go manual to manual it's only ~30 lbs, and if you go power borgeson to power rack it's only around 40 lbs. So I was off by 10 lbs on the stock power stuff to manual rack and the Borgeson to power rack is on the high end of what I said.
Now, if we can get power rack, power rack plus it's pump/brackets/pulleys/junk, and more Borgeson box measurements we can narrow it down with more accurate numbers. I would be willing to be the RMS K is pretty close to the same as what the HDK weighs though.