Since one can order just a shift lever over the counter, the factory probably thinks the epoxy is a permanent solution and welding isn't required.
Fully assembled in the shift housing, the shift lever tab/hook must align with the corresponding 5th/reverse tabs on the top carrier plate. If the lever separates, merely removing and welding the two pieces doesn't ensure correct alignment with these tabs. To verify correctly alignment, temporarily glue the two lever pieces (JB Weld or equivalent), then remove and weld. If you trust other alignment methods (e.g. eyeball, marking, etc.) go for it.
A tack weld in two spots is more than sufficient.
Sherwood