I ordered the poly bushings from Energy and just one look at them I knew they wouldn't work. Number of bushings, diameters, fasteners, etc. we're all wrong. It's a generic set of bushings and not specific to my car ('68 convertible) at all. I sent it back and got the rubber bushings and have not had any issues.
Take note that these bushing sets typically do not include the 2 bushings for the radiator core support for some reason. You'll also need to loosen the core supports when replacing the other bushings to prevent damaging your front fenders.
The only problem I had when replacing mine were the ones at the very back of the frame - the bolts were fused to the weld nuts on the body and there is no access to them. They broke loose and just spun, so I had to drill access holes in the trunk floor and then used blind grommets to seal the holes. See attached pics.
1968 Impala SS