ishaq, as far as I am aware the bottom ends are the same general dimensions (bar the conrod thickness differences), but get the old sump and compare it to a 16v 4a-ge to make sure.
seems decent enough but if I were you i'd bring along a mechanic to take off the old cracked sump and check if the engine was started with no oil...then the usual problem of the 20V would appear in the form of a fu**ed crank...
there are plenty of the silvertop and blacktop engines about with screwed bottom ends so you just need to find someone and get the sump of the bolloxed engine