This is a follow up on my earlier question on changing to a different job while I-485 is pending.
I understand from your response that a new Perm labor cert will have to be filed for a different job but the earlier priority date can be maintained.
I know that it is taking a long time to process perm these days. If the perm process or subsequent I-140 is not processed before my current H1B visa expiration date, would I be able to apply for H1B extension (for 3 years) based on the earlier approval of I-140 (which was for my old job)?

Thanks in advance