Quick answer, yes, absolutely.
Variables: Is your target 5.0 seconds flat OR just in the 5's such as 5.9 seconds? Big huge difference.
My LS400 currently has gone 5.7 seconds 0-60 almost stock. Modified air cleaner and cold air induction, removed final mufflers, great air conditions. Factory rates car at 6.3 seconds. RWHP is about 225-230rwhp. Test weight of 4000 pounds with me in the car.
SC400s (1992-1994) dyno stock at around 175rwhp and weigh about 3800 with driver.(obviously depends on gas in tank, size of driver, stereo, junk, etc). So, you need around 40hp gained and or a quicker launch to get to my cars performance for 0-60mph.
Options:
BFI. Easy, cheap, probably makes 5rwhp. (35 to go)
Headers, exhaust, piggyback ECU and tune should do the trick.
Higher stall torque converter is a simple 1/2 second improvement with no power gains.
From there, you can do cams, port and polish heads and intake. Go with higher compression pistons. Probably another 30-50rwhp to be had with proper work. Staying NA and wanting max top end would probably need ITB or the newer intake manifold modified to work. Probably another 10-20rwhp there. With these mods and bypassing the fuel cut to allow 8000rpm operation you could theoretically make in the range of 400+ horsepower at the engine which should yield around 310 RWHP.
Of course to get there it would cost MORE than a turbosystem that could easily make 350rwhp+++.
