First of all you should be looking for a 'Cam Kit'. Comes with lifters AND valve springs to match the cam profile. Push rods MAY have to be custom if your engine block has been cut down, the heads are shaved or your rocker stands are 'non standard' in height (to tall or to short for the block\heads combination).
I went with a Comp Cams 292S flat tappet. Pulls nicley from about 1800-2000 to 6200 or so. Nice street cam with a mild 'lumpy idle'. You NEED a 'lumpy idle' for the proper sound in a Cobra.
This cam (as do most) requires inner valve springs which MUST be removed for the critical 20 to 30 minute breakin period. The inner springs are reinstalled after break in. The nice thing about a roller cam is no break in to speak off, minor at least. BUT, NO WAY I would run a roller solid for a street application, there for race only, as they WILL fail on the street. Certain EXPENSIVE options exist to make a roller 'live' under street duty. A hydraulic roller is a great option for the street, BIG dollars compared to flat tappet. Not to mention I don't care for a hydro cam anyway.
See my engine build thread for more information on breakin of a flat tappet cam.
Ernie