I have a Lunati 10200704 (60404) in my 340. I don't think I'd want to go any bigger for a car that's used frequently on the street. For a "weekend car" or a street/strip car I think you could still do a little more, but IMO anyway I think I'm at the limit for a daily driver. With 3.55's and 26" tires there's a bit of a flat spot if I just let the clutch out normally, to take off strong requires a bit of clutch slip and a rapid increase in rpm's and then it's more like launching than typical street driving. It's not horrible, but the next cam smaller would probably be easier to drive. That would put you at the top step of the three durations you listed, the cam I'm running is a bit past that top step.
Specs on the cam:
Lunati 10200704 (60404)
Basic Operating RPM Range:2,200-6,400
Duration at 050 inch Lift:234 int./242 exh.
Advertised Duration:276 int./284 exh.
Valve Lift:0.513 intake/0.533 exhaust
Lobe Separation (degrees):110
Specs on my engine/car
1968 340, .060" over, KB 243 pistons
compression 9.8:1
308 heads, 2.02/1.60, stage II ported and flowing 264 cfm @ .500"
Eddy air gap rpm intake
Holley 750 Ultra DP
Doug's headers
Lunati 10200704, 1.5 ratio crane ductile iron rockers
2.5" dual exhaust with dynomax ultra flow's
8 3/4 rear, 3.55's, 26" tall tires, 833 4 speed. All in a '74 Duster that's been converted over to '71 Demon parts with a decent amount of chassis stiffening. Probably 3,300 - 3,400 lbs realistically.
