New cam and heads for original 273?

I cant help with your heads question, but Dad and I put a comp cam and lifter kit in his 67 cuda, 273 4bbl. We also added a dbl roller timing chain/gears and new springs/ with retainers. Make sure you get the proper keepers(10*) with the retainers....it set us back a few days trying to figure out why the old keepers(7*) would barely hold the valves. Oh ya if you are going dbl roller you have to specify that as you will only get a single roller in the kit. Im kinda unsure on the terminology with cams, but duration relates to how long the valve is full open, and I believe lift is simply how big the lobe is or how much it lifts the valve.
Here is the comp cams link
http://www.compperformancegroupstor...e_Code=CC&Screen=PROD&Product_Code=CL20-246-4