I think you are going to have a harder time than you think installing oil squirters. The surface that they mate to has to be machined flat, threaded, and an orientation dowel hole has to be drilled as well.
The whole point of using a GE block is that you can get them for less than 500 bucks and that they are a quick swap for plug and play.
As far as putting your 1j pistons into the GE welll,,,,,,, I really dont know. I dont know about bore, piston deck height, dish volume or if the rings that are already mated to the 2j engine will line up and fit in the 1j piston. If you use new rings you will have to re-hone to get them to seat right.
It sounds to me like you are planning on doing more to the GE block than you need to. If you really want to have that stuff then look around for an aristo 2j block or something and use the pan off of your 1j.
I dont think you are looking in the right places for a 2jz GE block. Did you check on craigslist for a lexus partout? Look for lexus IS300 motors too....
"http://cgi.ebay.com/ebaymotors/91-95-Toyota-Supra-Lexus-SC300-GS300-3-0L-2JZGE-Engine_W0QQcmdZViewItemQQcategoryZ33615QQihZ020QQitemZ300158151142QQrdZ1QQsspagenameZWDVW"