Heya there Fletch!!!!
Ive forgotten where you'd gotten to with your car, so here's my list:
I think you'd already gotten a TS box and LSD in, so shim that diff out- a must. A decent clutch- put the two together, and you're nearly one grand down there.
As for your engine, it's hard to say "build one up", because it aint ever easy.
You've got V6 mounts, and a 2.5 in there.
My options?
a) Sacrifice your 2.5s sump and timing cover for a 24v with some pipes and an ECU- its a nigh on 280hp proposition, and very nice.
b) Buy a 12v 3.0 and warm it over.
c) find some four cylinder engine mounts and tailshaft and go 1.8 turbo slightly warmed up- 250hp quite easily done.
or, my favourite?
With a 2.5, you could get a TT setup happening on stock comp and without freshening the motor up- just kinda build up the externals with growth potential, get that done, and drive it while you save for internals.
So, manifolds, with thick flanges for hanging turbos, I'd figure around the $1200 mark (for two)
Turbos? Just go 2x GT28 off an SR20 or RB26. With 9:1 you could put 8-9 psi into it, enjoy the torque and stay safe.
Intercooler?
www.horsepowerinabox.com and other Zoom advertisers were offering something like $550 for bar and plate I/Cs of decent size-
Pipework? Turbo-I/C-T/B with a BOV plumbed into it youre talking maybe a grand.
ECU installed and tuned? Around 2500, depending on what you buy.
Fuel sys? injectors, and pump, maybe around $800
Your radiator will need some good freshening, making sure the thermos work properly will be a certainty.
Exhaust, dump pipes back, wont be cheap, but hey, it wont all happen over night, and if you start accumulating stuff as you go, rather than get it all in one hit, then you'll be sweet. Buy generic stuff you'll need no matter what- pump (and injectors if you stay12V)
With two of those smaller Nissan style GT28s, your boost ceiling will be around 15psi. Total airflow given good efficiency of everything else will be enough to pump out over 400hp, but you'll need a comp drop, rod cleanup, forgies and O Ringed liners to get the most out of it.
As Barry has shown us time and time again, and as my mechanic pointed out, these arent weak motors, and the stroke is so short in a V6, that the liners likely arent as prone to warping at the stress levels we're all likely to place on them, so I reckon you start sorting out prices and figure out how to get yourself a couple of haridryers hangin off each bank!