440 cid small block crate motor
Id rather take their basic engine build plan and have another shop do the work. Get the bare block bore it out so you have 426 + cubes, get a real nice port and polish job on those commando heads. Get better quality rods, maybe a shorter duration higher lift cam for better streetablity and lowend and go from there. I would expect to get 450 to the wheels with a build like that on pump gas.