Had that been vs It that had been

[ostap77]

"Had it been a real deal, he would be out of the class."

OR

"If it had been a real deal, he would be out of the class"

Are these grammar constructios interchangeable? Which one is more frequently used?

[Raymott]

"Had it been a real deal, he would be out of the class."

OR

"If it had been a real deal, he would be out of the class"

Are these grammar constructios interchangeable? Which one is more frequently used?

Yes they mean the same. The second is more commmon.