I've seen some aftermarket pilot bushings not drilled 100%, tighten up on shaft when installing. Remove clutch assembly, reinstall bellhousing and try to install the tranny. If it doesn't fit, you might have to hand file or hone the bushing. If it does fit, take the tranny out and try to slide the disc on the splines. Sometimes there are burrs at the end of the disc splines that keep it from sliding all the way on. Again, hand file as needed. Reassembly, have a beer.