Will a 4L80e transmission out of 94 Chevy 3500 fit in 98 1500?

No, a 4L80E from a 1994 Chevy 3500 will almost certainly not fit directly into a 1998 Chevy 1500. While both trucks might use a 4L80E, the differences in the chassis, engine mounts, and crossmember locations between a heavy-duty 3500 and a lighter-duty 1500 are significant enough to prevent a simple swap. You'd need extensive modifications, likely including a new transmission crossmember, driveshaft, and potentially modifications to the engine mounts and possibly the body to make it work. It's a very involved project, far beyond a simple bolt-in swap.