i,ve used off the shelf mains in one of my 490,s , they actually have the same #as the oem ,BUT one big thing to watch is the radius on the crank where they butt up to , measure the distance to the end of the crank before removing the oldies , then check if u have the same after u fit the newies , (the off the shelf bearings had less chamfer than the oem , on the flywheel side i have used std oil seals , one facing in one facing out , as there was a bit of room , (i couldn,t get the oem ones in time ), on the primary side oem , all the bully,s i have , have over the counter main bearings , sometimes come as sealed units , remove the seals