R34, The non intercooled FJ had a .63A/R rear housing on a T03 mount flange. The intercooled FJ had a .48A/R.
As it's fairly well known, I bought the DR recently from Qld and I'm going to use it as a track/hillclimb car.
The sky is the limit as to what you want to do, but the first thing you do is punt the ECU and get an a/mkt tuneable unit, then bigger exhaust, then bigger or more efficient intercooler (bigger isn't necessarily better) then injectors, all depending on your budget.
I think personally a 2871R is too small as I think it will run out of puff up towards the red line.
I'm going with, as stagefummer suggests, an GT3076R with external wastegate and .86A/R rear along with 3" exhaust & 550cc injectors in a custom O'Ring fuel rail. With this I'm looking towards 400+HP at the wheels and then your problem is getting it to the ground effectively.
My only concern with Hypergear is it sounds too cheap, remember all of the Monsta T70 turbos that flooded ebay a couple of years ago, they were claimed to be ex USA but in fact were coming out of China, into USA and then to OZ and they were farked, would not spool up at all. Just be sure what your buying as cheap usually is.
Cheers, D