Just finished doing a rebuild on my '89 3.0.

As far as the oil pump in concerned, if you feel like pulling it out, which means pulling the pan, there is a detailed inspection procedure in the FSM that will tell you if it is worn or not. Mine had 125k on it and was fine, just cleaned it up and put a new front main seal in it.

I replaced the water pump, idler pully assembly (which includes the top coolant pipe, goes into the intake manifold), the tensioner assembly, and the belt (of course).

The belt, tensioner, and idler pulley assembly all came as a kit from Gates. I picked it up on RockAuto.com for $120, #TCK240.

The water pump I used was a Beck Arnley pump, #1312083. It was the exact same pump that I took off of the motor, same casting numbers, found that out after I got the replacement and was comparing the two. My motor had the timing belt replaced at some point, so, I am assuming the pump as aftermarket as well.

On this board, and others, it has been advised that you only use a factory Toyota thermostat. I took that advise and purchased one at the dealer, just to be sure. The 3.0 does not have the same issue as the 22R (or is it E's, not sure) where the thermostat needs a little piggy-back, mini-me thermostat in the flange. It looked like the one I had the guy pull at Kragen, but, what the hell, keeps the dealer in business.....

One thing I found in my investigations for this rebuld is that there appears to be some issue with how much you torque the crank bolt that holds on the balancer and the lower timing chain sprocket. If you look on Yotatech.com you will find many posts from people who had a timing belt service and then the bolt loosened up / fell out and then destroyed the pulleys and the snout of the crank, which is pretty much a bad thing, very bad.

I found this out after I had torqued it to 185 ft-lbs, as my '89 FSM says. The information I found said that Toyota changed the torque value to 217 ft-lbs and labeled the crank bolt as one time use, have to replace. I took the middle road, re-used the bolt, but went back in and re-torqued it to 217 ft-lbs and used lock-tite on it. Not sure how much a new bolt costs, but, it is definitly a Toyota only bolt, it has big flange on it, looks industrial strength.

So far, no issues, but, time will tell....