There was a reason for the block/transmission serial number matching. The Hydramatic drive fluid coupling torus (which was not a torque converter, BTW) was extremely sensitive to runout between the crankshaft centerline and the trans input shaft. Engines and transmissions were matched up exactly inline by using offset dowel pins where the bellhousing adapter ring attached to the block. There's even a pretty detailed runout checking procedure in the shop manuals, using a fixture that bolted to the crankshaft hub and a dial indicator.
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!