[astr]

There are no weights on the flywheel so the engine must be internally balanced.

Keep in mind that the starter mounts from the front on the 4BD1/2 so, if you move the flywheel back with a spacer, you will need to consider the starter meshing with the ring gear on the flywheel. From what little I can tell from the manual, the flex plate for the automatic transmission has the starter ring gear mounted to it so you may be able to sandwich a flex plate between your spacer and the crankshaft to provide a properly located ring gear for the starter.