The undispited king of the engines that went into those cars and the most desirable was the BOSS engine.
Brand new boss heads are being reproduced and these new heads fit the standard 429/460 block ,John Kaase fixed all the problems that was associated with these heads in a street car,soo far with a N/A set up he has hit a conservative 980 hp with a carb and it was well over 500 ft lbs of torque at 2000 rpm.
Plus there is nothing short of jaw drops when you pop the hood.
I am just throwin that out there ,at the end of the day ,I would hate to think for another 1500 bucks you could have double the hp if wanted and the shock and awe of a boss under the hood.
Take a gander at these pics........
429 boss engine - Google Image Search