Ron, old GM parts books (Buick/Olds/Chevy) show exact part number matches of some colors for the upper trim pieces on the '66-67 2-dr A bodies. I don't have books on Pontiacs for these years, but the matches likely still apply.
Buick calls the 2-upper pieces Back Window Trim Finishing Lace. The RH piece in black is GM part no 7587060. LH is 7587061.
Could not find part numbers for the bottom piece. Apparently it was supplied only as part of the rear shelf trim panel. Buick described this panel as Rear Compartment Shelf Foundation & Trim. Again there are exact matches to Olds and Chevy. The GM part no is 7607174 for black.
Hopefully a vendor can match some of these OEM numbers to parts in their kit, even if they are not familiar with Buick applications. In any case the pieces from another '66-67 A body 2-dr HT or 2-dr sedan should fit. Some colors may not match between brands however.
Here is an item from YearOne which gives one dimension to check for Buicks:
YEARONE Classic Car Parts for American Muscle Cars | Barracuda Cuda Challenger Charger Chevelle Road Runner Camaro Super Bee Dart Duster Valiant Firebird GTO Cutlass 442 Mustang Nova GM Truck Skylark GS Monte Carlo El Camino Mopar Chevy
Thank you Todd , for your very informative and comprehensive reply ,l believe most of these trim kits for 66/67 years are the same, the person who replied to my email at Ecklers obviously has no idea, but Year One list a trim kit for half the price of Ecklers cheers Ron