[Accelo]

Yes you can keep your 1969 front cross-member. The location of the clips is the only difference I know of. If you bolt the purchased clips into the front location you should be good.

71 or 72 brake lines and they will fit a 1969 frame and cross member? And will those clips work?
Yes they will work, exactly the set up I used. My issue was getting the lines to match up with the master cylinder. I would use inline tube. You have the best chance of getting it correct that way.

1969 differential I understand it is a different width compared to the 71-72 differentials, so does that mean I should get rear brake lines for a 67-70 in order for them to fit correctly?
You need to purchase the lines for the differential case you are using. So the back half would be for the earlier truck. The difference is the attachment points for the lines and the width. The earlier truck uses an off center rubber hose to feed the differential. The later truck has the attachment points in the middle. The hose is moved to the frame cross member from the frame. Both the frame attachment points and the differential points are different. Since you are keeping the 1969 differential it would be easier to stay with that system. That also keeps the line lengths correct for your wider differential. However, I can't confirm the 1/4" lines join at the same location in the front?

I hated working with lines because there seems to be so many options. I wish you luck sir.
Cheers.