Welcome to the forum
Yes, any Vulcan 3.0l engine can be swapped for another Vulcan 3.0l engine.
You just want the block and heads from the '91
You will use the intake manifold, timing chain cover, crank pulley, Cam position Synchro, oil pan/oil pickup screen, and all accessories from the 2001 3.0l on the '91
'91 used a distributor, 2001 needs Crank Position sensor, which is why the timing cover and crank pulley needs to be swapped, and the distributor removed and the Cam sensor synchro used in its place