Been watching this show for 40 years in reruns and never knew there was another verse to the theme song. Seen two variations on the dvd collection so far. In syndication we see the Clampetts driving down the street in Beverly Hills past palm trees as the actor credits appear for each character and then Jed points at something, and that's it.
In one version Jed is pointing at a semi truck with Winston cigaretes painted on the side as they pass it:

Now come along and visit with the Clampett family
They'll take you to their mansion in the hills of Beverly
And when they do you'll run into a friend of theirs the've met
That good old friend with filter flint, Winston cigarettes
Winston tastes good like a cigarette should

The other version Jed is pointing at a Kellogg's Corn Flakes billboard:

Now come along and visit with the Clampett family
As they learn the simple pleasures of the hills of Beverly
And that includes the products of your sponsor of the week
The cereals of Kellogg's, Kellogg's of Battle Creek
K, E, double L, O, double good
Kellogg's best to you

A lot of old shows had the characters doing ads for their sponsors, including Fred Flintstone in a cigarette ad.

I have a hard time seeing Jed smoking tabackky with sissy filters on em'.

One of the discs has a Winston commercial where Jed comes into the kitchen:
"Granny, where's that carton of Winston cigarettes I just bought in the new crush-proof packs?"
Granny took them all out of the packs and put them in a big jar so she could use the packs for something else. Jed lights one up, takes a drag and says something like, "Winston tastes good like a cigarette should."
Another ad has Jethro reading The Night Before Christmas("Was...the...night...before...Christ...Christmas") by the fireplace while eating a bowl of Kellogg's Corn Flakes.