yep i was a sucker for this.
had half a 4age in my garage for a year, with "the big build" in mind.
sold it all, bought a complete 4age had it in within 3 months. winnah!
bingo!
all your money spent might not gain as much as you think (unfortunately). especailly considering that standard ecus are tuned very well. and what your talking about isnt that much different from standard.
my suggestions, start with a decent engine. put in a thin head gasket, replace all the other gaskets, and easily replaceable stuff (water pump, maybe oil pump if its stuffed) all the other seals.
put it in and drive!
then if your keen, get another 4age cheap for the monster build up. 4kc's suck to much to be spending years building a 4age