i have an 88 wagoneer,... different tail lights but,...
on the wagoneer and many other projects
i have used 3M Strip Caulk
comes in long blue box
caulk is sticky, black, and approx 1/4" or less around
lying on wax sheets
wet your hands to prevent it from sticking to you
you can shape it how you want and form a seal or gasket
if you want your housing or lens
to come off a little easier when you remove it
you can put vaseline or some grease on the part that contacts the strip caulk, and it will release easier, you can push the housing etc onto or into the strip caulk to seal it better.
hope this helps.
dave in NC