I LOL'd when I read this Dave. The bore is different halfway through and is not threaded all the way through I know this as I shortened S-L-I-X's drop links and fitted them on here to discover the same thing. Luckily I have an ARC welder and was able to re-weld them as it's only mild steel.
I chopped the threaded bit in half, angle grinded the bottom part (non tapped end) then welded the tapped end back on.
In short, been there, done that, got the t-shirt and LOL when other people find out the same thing due to people not spreading the word.