Well, I took the time to look at Comp, Lunati, Crane and Hughes and there isn't a cam in the bunch that isn't too large.

The original Duntov cam for 283 chevy had about 220 degrees duration at 50 and about 0.400 lift. I imagine you'll end up around there.

Keep in mind that the 273 heads have pretty small ports and may need a little more duration than one would think.

Racer Brown is a good choice as there is a world of Mopar knowledge there.

R.