Her's one approach which solves the endianness and ascii/binary conversion:
void setup()
{
Serial.begin(57600);
float f = strtof("429C0000");
Serial.println(f);
}
float strtof(char *s)
{
unsigned long ul = strtoul(s,0,16);
float f = *(float *)&ul;
return f;
}
void loop()
{
}