I have a NHRA blueprint spec from the late 1970s for a 1969 340 that lists the cam duration at 336°/348°. The Chrysler cams had a lot of duration, not sure of other brands. I think the old White Performance Book had a section on these specs, if anyone still has one of those. Mine fell apart but I put them into individual folders like they were originally.

I also have an old Cam Dynamics "7000 series" stocker cam for a 340 that met the duration specs. Still in the original box. Maybe I should stick it on Ebag and label it NOS!