RB VS B Blocks

I'm fixing to try the 230 cold weather block 1971 casting that was produced in sept. and see what it does producing it into a 451 with a 69 440 steel crank I'm hoping to get some je slugs and some flat tops or dished...2" super comps fenderwells turned around backwards with 2 hairdryers(small ones)64-76mm...trying to get a fast time at track...daylight to dark in 5 seconds