Have you looked on the KYB website for information and other models the shocks might fit? Looked in RockAuto for shocks, too?
In other many threads in here, over the decades, there were complaints that many then-available shocks were too weak for a Chrysler's weight. The usual ones everybody mentioned as "being strong enough" were the KYBs.
There are THREE levels of gas shocks. The basic "low pressure", with about 15psi of gas pressure, so they are easy to compress to install. KYB is a "medium pressure" shock which might require removal of lower control arms on "Slab" '66-'68 cars. With Bilstein being of the "high pressure" variation. The bulk of gas shocks come with a tie-string to keep them compressed, so at the last moment of installation, the string is cut/removed and hopefully the top of the shock is aimed correctly to the hole it is supposed to index with/into. Several threads in here on the KYB installation in '66-'68 cars.
When your car was built (and into later years), Monroe was the main shock absorber supplier to Chrysler Corp. Even in Chrysler Parts, too. The current Monroe OESpectrum shock is a version of their Sensa-Trac shocks from the 1990s and such. The do still build a MonroeMatic shock that might be decent. Not sure of the valving, though, on the front shocks.
Keep us updated on your progress and results.
CBODY67