I use a parts catalogue on CD very similar to the repair manual except it has all the Toyota part No`s. If I need a part I just phone through the part number. Before I had the catalogue some years ago I had the head off and needed the water by-pass union/pipe that’s right at the back of the cylinder head, mine had corroded away in places. I gave the description to the Toyota parts manager and in a few days a washer arrived, no metal pipe or nut. Apparently the part I needed requires to be ordered with 3 part No`s.
90401-22004 for the union
90430-22008 (2 off) for the gaskets
90405-17995 for the metal pipe
With the parts catalogue on CD its so much easer to get the right part first time, it also has diagrams showing where ever nut and bolt is located with each part No`s. Not sure if they are available in the US, the link below is for one on ebay UK.
http://cgi.ebay.co.uk/TOYOTA-ELECTRONIC-PARTS-CATALOGUE-EPC-5-CDs_W0QQitemZ250069576904QQihZ015QQcategoryZ36086Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem