When Shelby started the Cobra, they had the 260 cid small block and shortly after they were all the 289 cid SB. Since that time, the 302 cid later called the 5.0 ltr replace the 289. Ford also made two taller deck 351 cid. The Cleveland and the Windsor, with the later being the taller deck height. The 5.0 is commonly stroked to 347 cid, and with an aftermarket 4.125 bore block, you can take it to over 360 cid. Likewise with the 351 Windsor it is commonly stroked to over 400 cid, and with an aftermarket 4.125" bore a 427 cid is common. It can be punched to 4.155, and it will go over 450 cid. Pretty big for a small block.
The 427 Cobra came with both 428 and 427 engines. This family of engines are call FE. In their cast iron form, quite heavy. All aluminum is almost as light a a SB. These engines are commonly stroked to 482 cid and can go bigger. Ford later made a 429 cid and 460 cid engine family called the 385 series. These BBs are physically larger than the FE engines. They are commonly stroked to 532 cid. The 385 series is arguably the lowest cost easiest engine to make huge power, but it takes a shoe horn and magic mirrors to fit one in a Cobra, but it is done. The FE is arguably the most expensive engine option, and it is a very complex design that required more talent to build. It has a lot of reliability issues, mostly caused by builders who are not up to building an FE. They can be just as reliable as any other engine when built correctly, other than an annoying tendency to mark its territory pissing
oil (most but not all).
Bottom line SB are lighter without spending big dollars for an aluminum block. Less cubic inches means less torque. Although, if you want to, you can make as much power, with less torque, by spinning lots of RPMs, it makes a finicky street engine with bad manors. You can build a SB with more cid than an original 427 Cobra, and have torque and Hp that would make an original envious.
So in summary, you have options out the wazoo! I did not mention 351/400 modified truck engines or more modern (now obsolete) modular engines. The new Coyote is even an option.