JAMES GARNER, his pants hitched up to a pair of extra-large love handles, cozies up to Sally Fields, her lean little body poured into jeans that fit like the wax on a store-bought cucumber.

The improbable lovers enjoy a May-December courtship in "Murphy's Romance," a determinedly folksy movie full of cowpie heehaws and other country whimsy.

Garner plays Murphy, one of the goll- darndest, good-naturedest geezers in all of the American West, an in-depth, aging version of Garner's Polaroid Guy. Only it takes a while for anything to develop in this slow-moving romance that's as sticky as a summer day when the gnats are swarming and as slow as a stalled porch swing.

The forthright Fields plays Emma Moriarty, a 33-year-old divorc,e who starts up a ranch with her 12-year-old son (Corey Haim) and succeeds, thanks to the good-neighborly intervention of 60-year-old Murphy, and, of course, her own pluck. It's sort of like "Wide Open Spaces in the Heart," with Fields mucking stalls instead of picking cotton.

Fields, as up as the Flying Nun and twice as sassy, sashays through this empty movie, set in an idyllic, sugar-coated Arizona burg full of kindly oldsters and well-behaved teens. By comparison, Hooterville was the essence of urban squalor and Mayberry a hotbed of sin and loose morality.

Martin Ritt directs the screenplay by Harriet Frank Jr. and Irving Ravetch, who cross the country wisdom of Tennessee Ernie Ford with the stale wit of the Johnny Carson joke team. Example: "Are you always this cheery in the morning?" asks Emma. "If I eat my prunes and the market edges up," Murphy replies.

Later, as affection grows, Murphy soothes her worries over their age difference with an axiom: "If the fruit hangs on the tree long enough, it gets ripe." It can also get soft and mushy like "Murphy's Romance."