so i'm rebuilding my original 1970 340

hughes rockers and you have not picked heads --gimme a break
chevy crank pins and long rods = lighter
even so I'd go 4" or longer
jones cam if you want to rev
light valvetrain, valves, retainers, springs
set up for 1.8 or 2"
ask krooser about lifters, springs he just looked at everything