Well. The next tank came to 16.11mpg. A marked improvement despite several trips up the mountain to make use of 4Lo in deep snow.

just for s&g I'll add some to this.
my last tank was 19.5mpg, with 150miles of it on dirt roads, some sideways, some in 4lo, but always with the throttle. This next tank is looking like 18mpg. Seems 16-19mpg is what I average, winter to summer. haven't bothered to see what nice and easy on the highway produces, but 75-80mph is good for 18mpg or so.

4,3 is a good motor but not known for its FE. My Dad had a '92 S-dime 2wd longbed extended cab with 5-speed but no other frills and though he's a relatively calm driver never could break 20mpg even driving superslab from Sacramento to the Bay Area (roughly a 2 hour drive), despite being rated 22mpg highway.