Generally
An additional earth braid between the engine block and the frame. This one has 11.6mm ring cable lugs on both ends. This is a solid ground braid of the highest quality. The length is 310mm measured center - center in the holes, the width of the braided part is 22mm. Do you have poor speed on the starter motor? Do you have strange temp and oil pressure gauges? It can be as simple as an earth fault, feel free to fit an extra earth cable. 2 pieces will be twice as good! Have you considered that you should have a good ground between the frame and the body as well, especially on renovated frame-lifted cars where it is painted with both base color and cover color, then you can miss the fact that there must be contact between the body and frame. Install a ground wire there as well.
