Go to IH8MUD for the most info on the 70 series LC. They have a sub forum specifically for these. I gather that the L engine is pretty much a dog with not much HP or torque for a heavy wagon. Some of them have a bad rep for blowing up too.
if its an LJ77 it should have a 3L naturally aspirated engine. The 3L is quite reliable but very very slow and you won't be doing any towing. If it's an LJ78 then it should have a 2LTE and they are slow and have a tendency to grenade. These are both light duty models in the Land Cruiser line up btw. Their heavy duty brothers are the BJ7x, HJ7x, HZJ7x, HDJ7x, and VDJ7x. The heavy duty line up I should note are almost bulletproof.