Welcome Dan,
215s are 1 or 2 sizes over stock, should fit fine, but is still a small tire.
Do you plan on wheeling this Samurai? or is it a highway transportation
vehicle? I would stay away from bigger tires if you are just using it for
transport, power is an issue on these little trucks.
The rear main seal is not usually a problem on these trucks, but if you
see a little leaking, when the trans is out is a good time to do it.
The pan gasket is a pain to change in the truck, it is best to use
gray silicone for pan gaskets, not the cork type, cork will leak in a
year or less, and the factory uses gray silicone also, just stick with it.
Wild