Call again- - - -I can loan you the right measuring tools to do the job accurately. Also, it's possible you have one bearing shell that's incorrect- - - - -slightly undersize. Don't be afraid to "shoeshine" the crankshaft a little with a long strip of cloth-backed sandpaper if necessary, but only after getting an accurate measurement. Dial or digital calipers just don't make the cut!

Edit: Is the engine still in the frame, or have you done enough disassembly to get an inside diameter measurement of the main bearing bore, the bearing ID, and the crankshaft? Trying to do accurate measurements with the crank still in the block will be difficult, if not impossible. The block bore specification for the #4 main is 2.969"-2.970".
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!