the latch on the driver side seatback is starting to fail; 60/40 split bench; looking for diagram and or info to repair

YES....these are troublesome....you have to take the seat completely out....undo the upholstery clips and take the skin off of there....WELD in fact weld "scab plates" over the cracked sections....I personally HAVE done this for THIS truck...is not impossible, but perhaps a bit fiddly....be sure to have plenty of time....these fatigue cracks will get worse and worse until they are mended~

admittedly did not take the WHOLE skin off, just enough to grind and weld the fatigue areas~

no one wants to show the "bones" of the framework.....it's like the best kept secret....or perhaps they are ashamed of their alloys~