Image Wheels Ltd has got 15" and 17" halibrands.
original size tires 235/60r15 & 295/50r15 hard to find.
i suggest to use 17" wheels.
i've used 225/50r17 & 245/45r17 on my fist three scratch builts.
i'll get "boyd coddington smoothie ii" 17x9.5 & 17x8 wheels, 275/40r17 & 245/45r17 tires for #4.
standart outside diameter of tire on cobra is 26" 660mm
peace and good luck,
Ozgur