Interesting about the solid lifters. I bought my car used and the builder originally put a Hyd 600 lift cam in it. He wanted the sound so he switched it out for a solid cam for the "noise effect". With the exhaust you cannot tell the difference at all between the the two cams. This year I was running the car around without the tunnel due to repair work and that is the first time I could actually here the lifters along with a bunch of other noises mixed it... sounds terrible, cant wait to re-installed the tunnel.
As far as carb choice, yes, a 750 would be best.
I have two of them I just put up for sale on Craigslist if you have any interest.
USED: Holley 750 Double pumper with Vacuum secondaries
Holley Carbs
NEW: Davinci Holley 750HP with Mechanical Secondaries
Davinci 750 HP Holley Carb/Brand New
Good luck and congratulations on building your Cobra. What kit are you going to use? I will vouch for ERA if you want a great riding quality car and AWESOME customer service.
Dave