cam shaft

The difference is in lift, duration, and overlap.

I had one with .509 lift in my 71 Duster with a 340, needed a lot of stall and 3.91 gears to act right....I didn't think it was very "streetable".

Now I have the one with .484 lift in my 73 Swinger 340 with 3.23 gears. Good street manners, decent gas mileage but less power.

There are trade-offs, depends what you are looking for.