Hi Aussie Dodge, I had a bad experience with my bearings, had a vintage motor expert do the job with the single grove big end and mains, the big ends did not last long and the mains were real tight, you definitley need the x or you will have trouble, I replaced my big ends with a set of used bearings and bought a dremmel and did my own x on the mains so I have a grove and a x , as mentioned by Robert schamfer the bearing edges and make sure the 3 groves on the sides are there if not use small round file do it yourself. Some experts should never be allowed to touch these old motors. My engine runs great even cruisers at 40-45 mph for more than 30min no over heating. This is the place to ask these questions because most of us have been there. regards Brian