The reason for the switch to the tang at the parting line for the upper bearing is that it's much easier to change main bearings that way. The bearings with the upper dowel pin make it necessary to lower the crankshaft more than half an inch to get the upper shell out. That requires removing the timing cover and all the main bearing caps at once. The ones with the tab at the parting line only need the crank to be lowered a few thousandths to release the squeeze on the upper bearing shell, and a cotter pin inserted into the oil hole in the crankshaft to roll them out.
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!