I put down 440hp and 475 torque in my turbocharged L28 which I still have, there is no need for SBC Chevy conversions, BMW or LSX swaps. 400hp in a Datsun is a handful, yet reliable.
Installing a RB25 or RB26 is not for the feint of heart and buying the engine just by itself is an easy $4-5k with the matching transmission.
Here is my bored, stroked, higher compression and turbocharged L28.
