The most obvious shocks that come to my mind are the Edelbrock which are used on the stock Kirkham. They are relatively inexpensive and are quite good. They come stock with 600lbs springs rear and 400lbs front. I don't think the Konis' are available anymore. You next choice which is probably the best shock available for the Cobra is the Penske racing shock with remote reservoir. the last time I checked, they were about $2500 for the set. Stay away from Spax, JUNK JUNK JUNK. I bought a set for my 428 and one just broke when we lifted the car on the hoist. CMCCART, where are you in the US? I might be able to help you finding somebody for your tank!
Emmanuel