Can a 400BBM w/cheap aluminum heads compete/dominate against the street LS?

Speed disaster 4.25 crank

Mostly...the heads are where your problem is. Porting isn't cheap.
CID is cheaper.
451 LD with decent heads will dust a 408 ls...but in what..? A sleeper race car? bone stock? Neon ground effects and mixed up bolt ons by a teenager...?

Imo/ime A good small block 410 will put a hurting on them when setup right... but pick where. Light to light. Freeway or .. cause you cannot have it all or cheaply at least .