I drive a small block with a TKO 600 and a 8.8 rear end so my driving expertises with an FE Cobra is limited. I have driven Coach Mike 428/461 KC Cobra and Mike Lainhart 427/487 KC Cobra several hundred miles each. I have been the passenger for a few thousand miles. Both Cobras have Tremec 5 speeds. Lainhart's Cobra will cruise at 1800 -1900 with no trailer hitch jerk. Coach has to stay 2100 or better.
I would suggest you us the auto math calculators to give you an idea of what speed/rpm range you will use most. It just an guess at the best. Each motor is different. Tire size, motor rpm, torque, cam, rear end ratio, gear ratio of the trannie all play into the equation. Most of the toploader big block I know of cruise at 2800 + - range.
Cruise speed can be 50 mph or 60 mph or 70 mph or 80. Think about which speed you will drive the most and pick a setup that is comfortable for you.
If you drive your Cobra a lot (every week) a good cruise speed is very important but if you only drive it a few times a month you can put up with the high rpms or jerking.
But what ever, it's the ride of a life time.
Oh yea, I have 23,500 miles on my small block and I'm getting ready to drive 535 miles to London, Ohio. This will be the 7 TH time I drove to the DVSF/LCS.
See ya on the road.
Dwight