The sonotrode and anvil of copending application Ser. No. 12/925,652, for advanced ultrasonic welding of work pieces, are readily incorporated into new form-fill-seal machines, but existing machines with heat-seal stations pose difficult problems for swapping of the sealing packages. Kits enabling heat station replacement, with the further improved sonotrode and anvil disclosed herein, comprise: a housing; a linear rail fixed thereto; anvil and sonotrode support members; and a parallel gripper. Each of the anvil and sonotrode support members is slidably attached to the rail(s) and are also connected to a respective piston of the gripper, permitting actuation of each through cycling of the gripper pistons. The improved sonotrode/anvil combination each comprise a corresponding plurality of energy directors arranged into a three-dimensional grid pattern to produce a narrower weld region, but one exhibiting greater durability, thereby permitting use of less packaging material, and which may also weld a company logo into the workpieces.