make your mind up whether you want 280 or 400bhp, turbo choice would be a big thing between the two.
for 300bhp i'd just get a gt28rs, they're good for around 320bhp.
for 400 i'd look at a gtx2876r or a gt3071r, both low lag units,m although the 30 has more potential and lower temps.
t38 would be too big to get good response for 280 horses, would be about right to have the lag they produce for 400bhp though. consider a t34 if you want to save some coin, a 4wd cosworth turbo could get you around the 280 marker for proper budget item until you go further.
i have a gt3071r on mine on a 0.63 housing on my forged 2.1 zetec turbo, goes well and spooling well at 3500rpm.