['68OrangeSunshine]

Benbloom -- a Rockwell T-221 transfer case is unusual in a '69 K/10. I thought 1968 was the [first and-] last year for an SM 465/T221 set up. (With GMC and Canadian hold-outs until they ran out in '69.) With a Marin County location, the most statistically probable origin for a GM truck would be Fremont [code Z] across the Bay. But then we all know how these rigs get around.
Also after 40+ years, who knows what a PO may have cobbled together, just to get back on the road. You could even have the SM420 4-speed, also a Granny Gear tranny, but with even lower ranges in 1-2-3. Also you never use 1st [Granny] unless you have a full load of riprap in the bed. SM420s last production year was 1967.
The VIN would be helpful. Or a pic of the SPID. You can use X's for the last five numbers, if you're security conscious.

That being said, I have heard the Rockwell T221 was very noisy in its own right, even on a good day. I have a core SM465/T221 [that was misrepresented to me as a 205 by an long-gone junkie] I thought 1968 was the only year for that combo. I hear it's a strong TC but replacement parts are hard to get now.
One more thing, make sure the gear oil levels are up to spec. SAE 90 GL-5 will work. They get loud if the levels are too low. [Just before they burn out.]

GASoline71-- I remember premium ARCO selling for .25/GAL in Hollywood in 1969. We would've rioted if it was as high as .40!