Put jackstands under both sides of the k frame, and under both sides, in front of the front leafs. Get a 2x4 and a 4 or 6 foot level; level across both front fenders, using shims on the stands. Same for the rear, avross both rear fenders.
Then put level on door sills, level from front to rear with shims on stands. OK, this is how it was born at the factory.
Now, find some points to measure from, to a level floor(bottom of front sub, both sides, same with rear) 1/2 difference ? Put a 3/4" shim under the low stand, and weld in the connectors.