Mike, I spoke to this mate of mine today. He's not overly fussed on the A3s for a street application. He likes to see these heads used with nothing less than 380 cubes with a lot of rpms & compression... He built an A3 head Clevo a couple of months ago with 13:1 comp, .700+ solid roller, 383 cube. It made 660hp @ the flywheel at 7200rpm. The heads flowed 370cfm at .700 at 28". He couldn't remember the low-lift values, but he knew they would be less than your Ronnie Crawford 4Vs...
He said the manifold is a pain to find for an A3 / 9.2" combo. He had a "semi finished" Ernie Elliot manifold for that application. I assume that means it still needs to be port matched to suit.
Anyway, he said the heads can make good power for a specific application (usually drag racing these days), but he wouldn't use them for the street. That's not what I wanted to tell you, but he's built MANY cleveland motors.
He also questioned whether you really needed the SVO block. He builds .030 cleveland blocks converted to 4 bolt without grout that run mid 9s in a 3300lb car naturally aspirated. Granted, he does some pretty clever
oil passage revisions, but if you're not planning on going past 7000rpm, he doesn't think you need to spend the $$$ If we can get you to bolt a supercharger on, then that might change
My exhaust guy is awesome. He hadn't seen the car, and you'll notice in some photos how far the driver's footbox extends past the passenger. I forgot to tell him how hard it would be to miss the steering shaft, brake lines, engine mounts, starter motor AND an extra 8" of footbox
He took one look at it (for about 2 minutes) then drew me a diagram of which pipes would go where. Over the month that he had the car, the diagram never changed. It was perfect!!!! Clever guy!
If you want any more detail about Clevo combinations, I'd be happy to ask. I didn't really what to tell him about how you drive your Cobra, but I figured you weren't looking for a massive rpm / high compression motor for your street car...