Toyota Repair: 91 Toyota Truck 3.0, rod bearings, main bearings

Question
I understand that the bearing sizes go by a number system and  i am trying to replace my rod bearings, but im not sure how the  number system relates to standard .10 .20 ect. i read your answer on the 3.0 knock being the front main bearing and i am not sure if i should automatically go to a five or since mines a two i should just go to a three.  i have not actually  seen the main bearing just the rod bearings so i assume the mains and the rods are both two could i be wrong about this? please help because my auto parts stores know nothing about the numbers. Thankx deb

Answer
Your'e probably not going to get much help from any of the auto parts stores on this, both the rod and main bearings are numbered from one through five with the tightest bearing being the number five, this only applies to standard size bearings on the crankshaft and rods, if the crankshaft has been reground to an undersize in the past this does not apply. If the crankshaft rod and main bearing journals are standard and have not been reground then I would recommend installing a #5 main bearing on the #1 and increase the rest of them by one number, the same for the rod bearings, tighten them up by going one number higher than the number on the bearing, if the crankshaft has been reground to undersize the bearings will be stamped on the back 0.10 or 0.20, if not it will say STD.