What are your hp goals? Are you going to stick with the V8? If so, you may want to get in touch with RedPhoenix. He can hook you up with a manual trans swap kit which is a huge upgrade right off the bat.
For the ECU, contact
gazi_ali@hotmail.com. He is an excellent source for used Lexus parts and his prices are the best. I have bought lots and lots of stuff from him over the years between my SC300, SC400, and GS300.
Jeez, I sound like a vendor... Good luck, keep us posted.