Will a 1999 silverado truck engine fit in 1993 truck?

No, a 1999 Silverado engine will likely not fit directly into a 1993 Chevrolet truck without significant modifications, if at all. While both are Chevrolet trucks, the engine bays, mounting points, and ancillary components changed considerably between 1993 and 1999. Even if the engine displacement were the same, the differences in accessories (alternator, power steering pump, etc.) and their locations would create major incompatibility issues.