I wouldn't worry about the Lovejoy so much as I would relying on such a small end-face seam weld for power transmission. It might be more prudent to use a larger spline size lovejoy and lathe it to match a slightly larger size, then mill the spline adapter to include a keyway.
Of course that really depends on how much force it took to press the spline bushing into the lovejoy before you welded them together.
Relevant project link where the motor and transmission were coupled by interference fitting a spline adapter onto the motor shaft. Part was precisely machined so that it could be heated, pressed onto the shaft, and then cooled.
http://evdrive.com/BMW_project/ACmotor.html