What is the block on frame of an 1988 dodge Dakota where brake lines run in to and a lever spring system running down front rear drivers leaf spring?
That's the brake line bracket (sometimes called a brake line support or rear axle brake line mounting bracket). It's a metal bracket bolted to the frame near the rear axle, providing a secure mounting point for the brake lines and often incorporates a mounting point for the lever-type spring system you describe, which is part of the rear suspension's anti-sway or anti-roll bar linkage.