HTTP Basic Authentication Between F5 and Pool Members

Hello,

I would like to ask, which is the best method of authenticating user requests with HTTP Basic Authentication against the Pool Members, please?

Need to add, that I'm already using an iRule, that authorizes users with HTTP Basic Auth in the Client <-> F5 HTTP flow - works well without any issues. I just need to do it between F5 <-> Pool members with DIFFERENT username/password. I presume I need to change an Existing "Authorization: Basic" header.

I'm thinking some iRule (possibly HTTP_REQUEST_SEND event), or using a rewrite profile?

I'm using 11.5.4. This is LTM request only, no APM.

Thank you.

Jozef