probably not possible. 600 tq is alot, especially with 87. 408 takes a 6.0 block like you saw on Jegs Bored .030 over and a 4'' stroke crank. most 383 kits ive seen use the 5.3 blocks. not positive the stroke and bore. you could do a 500 hp build on 87 octane with a good motor maybe. but if you want that much torque, might want to look at diesel.