Playinghooky13

I found some answers to my questions on the forum I guess I should have looked before posting questions. But can I make this work by changing heads and cam or just heads? Sorry to bother 

Are the bottom ends of these engines the same? Meaning can we change the heads ?

Yes the old engine has the line between the heads. Yes the new engine has springed push tubes on the exhaust  valves 

I'm having some issues here and hopefully someone here could help me out. 

Ok this may be lengthy but here it goes.

We have an 01 mack dump truck with the e7 427 that spun a main so the owner decided to buy a used salvage yard engine which is a 2003 e7 427 we removed all of its exterior components and replaced them with the old ones. The "new" engine had Jake's the old didn't so we removed them. The engine cranks and idles great runs good on flat ground but loaded it's a dog. It will fall on its face on a hill loaded or unloaded also. We changed injectors with the old ones no change. Changed cac. Boots checked all piping and manifolds for leaks nothing. Old motor ran much better. This engine looked good no cam pitting or cylinder wear etc holds 60 psi oil pressure no blow by to speak of. The engine does not smoke abnormally just a little black under load but not much. All filters have been replaced etc. I'm not sure of the next direction. The engine shows to make at the most 12 to 14 psi of boost with the pedal on the floor. If anyone has any input I would really appreciate it. Thanks in advance