Would a 350 small block fit in 07 Chevy Cobalt?

No, a 350 small block Chevy engine will absolutely not fit in a 2007 Chevy Cobalt. The Cobalt was designed for much smaller, more compact engines. The 350 is significantly larger and wider, requiring a much larger engine bay. You'd have to do extensive, likely impossible, modifications to even attempt it, and the end result would be far from practical.