I would be looking for mid range power/torque and the aim is around 400 ish FWHP. Running an R154 box and 3.31 Jag power lock rear end with 315x17 rear tyres. Total car weight will be around 1,000kg.
Driving will be 50 /50 street and track days. Nothing serious.
Due to the way the exhaust exits the side of the body the primaries will be slightly un equal length.
I know it's not the best way to design the pipes but it's part of what makes these cars.
x2. And it would be worth your wild to have some stainless heat shielding!
Just you know... Use a nice transition to whatever size you use. Don't just jam it in there.
The original cobra 427sc had 2" pipes right to the collector. but that was a few more cubes than me.
If it won't make any difference going too big I will go 1 3/4" headers out to 2" 90 deg bends (to make it look original) where it goes out the body then to a 4 2" into 1 3 1/2" collector either side.
Heat shields are on the shopping list for registration but they do look better without them.
I saw a black Cobra pull up next to me in traffic today here in sunny California. I just stared at the side pipes and they were indeed huge but he had a huge engine by the sound of it. I'm sure you'll be able to fill them with the boost you will be pushing.
Get in contact with Scotty (aka Ozvenom on this forum and also Clubcobra) He has made a lot of sets of sidepipes and specialises in Cobra's with 1UZ's in them.