If he weren’t busy right now, he could help them.

=> Were.............................

If I were you, I would tell him the truth.
=> Were..............................

If I were rich, I could afford to buy an expensive car.
=> Were............................

I didn’t see the signal, so I didn’t stop.
=> Had............................

Would you visit me if I were sent to prison?
=> Were...........................

If the salary were high, the job would be worth doing.
=> Were...........................

If you change your mind, there will always be a job for you here.
=> Should................................

If you wish to take advantage of the offer, kindly tick the box on your order form.
=> Should.............................

If we hear any further news, we will be in touch immediately.
=> Should..............................

If you decide to accept the post, you will be expected to start work on 1st April.
=> Should....................................