Side by side, the Lexus SC300 / SC400 shocks are basically identical in uncompressed height (as seen in the last set of pictures). As I write this though, I realized that I didn't fully compress the Lexus shock to see how much more give it had.
This is where the Lexus shock will give us the most problem in terms of fitment. As you can see here, the spring seat is significantly higher than our spring seat (sorry, I forgot to take measurements). It appears to be about a 2-1/4" difference between ours and the Lexus unit. The other part that is concerning here (and I'd have to look at it again to make sure), is that the Lexus unit seems slanted. I believe this is due to them being specifically left / right units for the Lexus whereas our units are left or right. Perhaps cutting off a coil or two would be a potential fix for this as it would give the room needed to set the spring down? Though, I know that would cause a whole different set of issues with spring rates and whatnot.
However, if we find an insert adaptation like we did with the Mitsubishi Bilstein unit that's no longer available, I believe it will work without issue as the Lexus shock is fairly narrower than our unit.
Here, the fork and LCA point are
very close. I'd say shaving off about 1/8" of the LCA bushingg where the shock fork meets should do the trick. I did not check the bore hole of the shock's fork, so I'm not sure if the bore is too small, too big, or just right. If too small, the fix would be easy and just make it larger. If too big, adding washers ought to fix the issue.
The spring seat itself seems to be ever so slightly larger than the Vogtland spring. Like, it'll sit there, but it seems to require a small bit of force for it to actually set in there. I'm not sure if just forcing the spring on there during the compression phase of shock / spring / strut mount assembly would do the job or if a small amount of material would need to be shaved off where it makes contact. But shaving off material would - I imagine - be detrimental to the structural rigidity of the spring seat.
Both shocks fully extended. They are essentially identical in length with the Lexus unit being ever so slightly longer, maybe 1/2"? Note the top of the Lexus shock having a wider shaft tip. Perhaps for our application it could be ground down for it to work with our strut mounts. Or perhaps our strut mounts can be modified to work? Like earlier, I did not take measurements of that shaft tip.
I did however, take measurements to the shaft of the shock and piston body. The shock shaft came in at 1-25/32" (appx 1-7/8") diameter. As for the piston body, I got two measurements for it. The first was 31/64" (appox 3/8") and the second was 1/2". The reason for this was because the first measurement I was doing myself while also holding my phone to take a picture and the second was with one of the store sales people doing the measurement while I took the picture.