Hello Greg, there is a set of shims that load the bearing and go between the gearbox and the bell housing. Did you put exactly the same ones in, and was th new gasket exactly the same thickness. If you changed the bearing, then the shims may not be correct anyway.
I would slightly back off the bolts between the bell housing and the box just a touch and see if it frees up. Hopefully it's as simple as that? Then find or make some correct shimms.
I've had the slider springs come out inadvertently during assembly. The gearbox goes bang once a slider gets free and ends up breaking gear teeth. I always tripple check after that learning experience.
Good luck with it.