Yes, Bill and I have discussed the best matches for the 66 mounts over on V8. Likely some info here as well.
Dan, how close to original do you want?
If you want correct hardware (down to bolt head markings) AMK is the source. Inline tube may sell their products.
The Ground-up kit has nice hardware with flanged bolt heads that are sorta like originals.
Most bushing kits have the one-bushing-fits-all-locations. Ground up has a nice deal for it and the hardware. Get the convertible kit as it has the 2 extra cowl mounts we need for our Buicks:
https://www.ss396.com/chevelle/DCC-1515.htmlThe original Buick biscuits behind the rear wheels and at the trunk corners are a larger diameter than the other locations. We found some good matches from CARS and Restoration Specialties. Mounts over the rear axle are different too.... they are a push-in puck style and not the bolt-through style. You can buy those elsewhere too.
With all that said, the generic kits fit and work fine, they just don't look like the originals at all locations. To make it look 100% correct, you need to buy a few replacements.
Update to add link to Bill's V8Buick post:
https://v8buick.com/index.php?threads/my-66-gs-hardtop-body-mounts.290996/#post-2540037
