ally_p,
Rebuilding the 1JZ is another option if you are up for it.
As for a 1.5JZ, I did the following for it. 2.5MM Boost Logic HG, ARP Headstuds, New Oil Pump, Seals, Gaskets, Bigger Injectors, Bigger Turbo (from 1JZ Stock Twins), coolant pipe by the water pump (tad bit longer then stock...