A-Body leaf spring bushing challenge.

Thanks in advance for trying to help. I'm really frustrated with this, and I did a lot of research before posting. 1970 Duster 340 genuine H-code unmolested. Just started putting it back together after 3 years out for paint. Been acquiring parts for the last several years a little at a time. At some point I replaced the front spring eye bushings on the rear springs. These bushings were supposed to have come with the bolts but I can't find them now. Ordered a set of bolts from a popular Mopar supplier and these are way too big but are the only ones he lists. Another big Mopar supplier says the same thing, that these bolts fit all Mopar V8 cars. They don't. My car requires a bushing that is 1.5" OD to fit in the spring (not 1 and 3 eighths), but with a 1/2" bolt. The holes in the front hanger bracket are 1/2". Problem is all of the aftermarkets and even the big Mopar guys are lumping the applications together. If you look-up the bolt/bushing for 1970 A-Body you will find the same P/Ns that they list for all other bodies, and this is incorrect.
Right out of the 70-71 parts book all of this stuff (hanger/bushing/bolt/nut) is unique to A-body cars with any engine, and it's all 1/2". Interestingly the P/N for the nut is the same as for the U-bolt nuts (6023019) so the 5/8" bolts that the Mopar suppliers have are not only the wrong size (5/8 instead of 1/2) but at least the nuts are not "correct" either.
Now let's make it more difficult...regarding the bushings that I installed in the springs, the inside diameter is too small to accept a 5/8 bolt, and too big for 1/2". A closer look showed that the "tubes" in the bushings that the bolts go through have 3 little deals machined into each end of them (I'll call them knurls since NAPA lists their bushings as "not knurled"). It is these things that prevent a 5/8 bolt from fitting.
Now I don't know what to do to fix this. I don't think I'm going to find the correct parts anywhere. Drilling the holes in the hangers from 1/2 to 5/8 so that the new bolts fit seems logical, but because of the knurls in the bushings the bolts won't fit in them, or are the bushings designed so that you hammer the bolts in and the knurls hold them tight? I can't imagine this wouldn't ruin the threads though. Can I drill out the knurls so that the 5/8 bolts fit ? I don't want to un-engineer something that is there for a reason. If I have to remove the springs again to change the bushings "it is what it is" however I'm hoping not to have to spend all summer "trying and returning" over and over again since it appears that I cannot rely on the aftermarket listings for the bushings, or the bolts to be correct.
THANKS !!