for the best combination of HP and TQ, look into a 393 or 408 stroker kit. Almost all stroker kits are close to the same price, indepentant of cubic inches. For example a forged 396 kit and a forged 427 kit aren't far off in price. Don't get sucked into thinking the more displacement the better. There is a ton of research out there, here is a descent start
A 408 is planned for my buggy.