Gotta pull the oilpan, and wiggle the rod connected to the crank up and down. If there is noticeable play, remove the rod cap and inspect the bearing and most importantly the surface of the crank. If your lucky, you will still have a smooth surface on the crank. If so, replace the rod bearings with new ones (I suggest EB for 'em). However, keep in mind that this is only temporary, and the problem could still come back. Worst case scenario, you will then have to pull the motor, disassemble it, and get the crankshaft machined for the next oversized bearing. I am going to bet, that, once you pull the pan, that you will see remnants of the old timing chain (PO) guide stuck to the sump. And, if you do, plan on a rebuild.

BUT, that's not bad. $250 for machine work (block,crank,head) $250 for all new parts from EB,
You have a great motor. My first motor rebuild is in my 85 4Runner. FSM with step-by-step and torque settings, and you are golden. It really isn't hard at all. Whatever you find, or decide to do, I'll be rootin' for 'ya.