Slant 6 dies when driving

Buy a cigarette lighter voltmeter to monitor while driving. $15 digital display on Amazon or Harbor Freights cheap $6 one. Should see 12.6 V when off (battery full charged) and ~14.3 V when driving. At least your early fussing was with battery and charging. Such meter is essential for new cars since they give no dash monitor. I use in my 2002 T&C when I suspect charging problems (worn alt brushes recently) and try to monitor on long drives so we don't get stranded again (belt slipping at alt due to bad p.s. pulley). To determine O/F problems, see if a shot of starter fluid down the carb throat smooths it at idle. If so, you may have an air leak.