Cam lift ?

If your using stock 273 heads, you should keep the lift at around .450 because they really don't flow more air after .420 lift.
With this being the max lift you can run, just run way more duration.
My 273 heads stopped dead after .420 and then started going backwards at .450 lift.
They flowed 181.3 at .400 and 174.3 at .450 lift.
If you have a chance, flow your heads before you pick your cam.
I was talking to a amc racer at the track last week and he has to run a stock lift cam in his class ,but as much duration as he cares to.
I don't think you should go anywhere near this but it's an example of how to make power if your willing to run low gears and and high stall converter.
The duration @ 50 was 276.
How much gear are you willing to run and how much converter stall speed.
I would at least run a 3800 stall converter and a cam thats at least .241 @ 50 \\ you will have enough compresion at 10.5:1

You will run into detonation problems with a cam with any thing less then 240ish @50 :pale:
Pick your cam after you can know what those three things are.
(gear)
(stall speed)
(head flow)