My vote would be about a 500 to 512 stroker in the 400 block. 10.5 to 1 Ported Edelbrocks (jump on one of the deals on race section) A mild hydraulic roller cam (but milder cam for sure 230/236 ish @ .050 duration.) will make a good cruiser in a 505 will act like a 218/224 cam in a 400 cube. 5 speed and have plenty cruising fun. 750 3310 vacuum sec or an 800 edelbrock thunder series.
