There's an article here on replacing Superformance headlamps that may be worth checking out:
https://www.secondstrike.com/Technic...Conversion.pdf
Do you have sealed beam or interchangeable bulb headlamps?
The former is likely H6024 Wagner High/Low Beam Halogen (or equivalent). This is a standard 7" halogen sealed beam, available at any auto parts store - though it may be a different brand.
The latter probably takes H4 halogen bulbs. Again, these are available at any auto parts store.
It's worth pointing out there are standard replacements, but most bulb manufacturers also offer extra bright, higher color temperature or tinted bulbs. Some of these will have significantly shorter lifespan, though most Cobras don't use their headlamps enough for this to be a real problem, IMO.
Many will promote the use of H4 LED replacement bulbs as a way of improving their headlamps, but you should be aware using such bulbs in headlamps designed for halogen bulbs will render them non-compliant with DOT standards and therefore illegal for street use. Per this article:
"... buyers cannot simply replace the bulbs in a halogen headlight with HID [Note: or LED] bulbs. Instead, they must upgrade the entire headlight and ensure that it carries RoHS, CE, and E-Mark certifying its compliance with European standards. Or in United States, it needs to be DOT-Compliant to follow USA transportation regulation."
https://www.vehicode.com/blog/the-co...ght-bulbs.html