I have seen a couple of 1JZ RA23's so they do fit.
While the 1G can make plenty of power, aftermarket parts are hard to get. On the other hand, the 1JZ has a huge aftermarket support. For this reason alone, it's a good idea to look at the 1JZ.
Having said that, I am still a big fan of the 1G. Cheap thrills. I don't know too many $700 engines that will make 150 rwkW.