High 300 to low 400s not too hard but engine & transmission need be in good order.
Old engine best rebuilt with some forged pistons new oil pump etc. want a decent turbo such as gtx2867r, ported standard manifold, 3" elbow & good exhaust, recored top mount & post core WI or a front mount, CC clutch kit, larger injectors - maf - ecu or piggy back ecu, better fuel pump.
I've had 380 hp on standard young low mileage engines using scrap yard sourced evo injectors, z32 maf & 3kZX fuel pump & piggy back ecu, just don't get too hp greedy or cut corners as car is now old & 7 years laid up won't of helped.
Brakes & suspension will need bit of work too so review what you got with current R what you can spend & it's condition as a well built R for your usage is going be more fun even if only 300-330hp