I am going to do a bit of guessing here, assuming the compression of you engine is not very high ie 76cc chamber head short stroke.. going for a to radical cam would be a mistake in general the more radical you get (longer duration more overlap) the further you drive your dynamic compression down I would get your engine details nailed down and fill out cranes cam recommendation sheet they have more resources than most anyone here for a good cam recomendation. My experience with the simi stock 700 wasnt all that great but it was on the strip so it didnt show the advantage of the overdrive but it showed the disadvantage of the big ratio change from 1st to 2nd. On a stock unit 400 plus hp is pushing it. You would have to consult the nitrous experts in the other section Id be a little concerned with a 150 shot if you are planing on haveing 400hp n/a unless you bottom end is forged and a 4 bolt(factory 327s are 2 bolt).

 

if you do put L31 Vortec heads on the engine you will have to change the valve springs to run any camshaft with more than .450 lift .the factory springs bind @ .450, you can put springs made for a LS1 and get up to .550 lift , any more the rocker arm will hit the valve guide. but you can buy a very inexpensive tool from several speed parts companies (i.e. summit, jegs) that recutts the valve pocket and the guide to accept a standard SBC valve spring and run any camshaft you want.