what?There might have been a groove on the end of the crank. I've seen that with a few engines from just general wear. Its common enough where they make a sleeve that can slide over it and create a fresh surface for the bearing to seal on.
On my last motor build (not a 2J) I got lucky and had a spare crank as the machinist noticed it while they torqued everything down to take measurements.
Again, I don't know about the 2JZ engine (yet), but NAPA makes a fantastic product called "The right stuff" that is an AWESOME gasket maker. Its expensive but does one hell of a job. Maybe try cleaning up the seal surface really well and applying some of that stuff before placing the gasket.
http://www.alliedbearings.com/mfg_prod/seals/cr_speedi/cr_speedisleeve_install.pdfwhat?
How much would the rpm's drop while doing this? Would the car be hard to start?Have someone step on the clutch while the car is idling. You can usually hear the RPMs go down and the see the front balancer move in and out.