[Tommy]

If the guy(s) who was giving you advice was trying to sell you something, you ought to talk to someone else.
1. Drilled and slotted rotors aren't essential to good working brakes, especially for the street.
2. The front brakes do most of the work in stopping your car, so switching from drums to discs on the rear won't yield a noticeable improvement stopping IMO. It also won't put much heat into your rear brake rotors unless they are significantly undersized.
3. Lots of Cobra replicas, including mine, use factory style brakes designed for much heavier cars. Mine work fine even on the track with repeated max performance braking from 140 MPH.