Case 580C, 207D, backfire rough running

I'm kinda new to the forum hope I'm in the right place. I just purchased and installed a "rebuilt" engine in my backhoe it's a 207D in a 79 model Case 580C. I installed the engine and it runs a little rough and throws a backfire here and there with plenty of white fuel smoke. Contacted the place I bought it from and they sent me a set of new injectors Installed them and no difference. Then they sent me my old injector pump back installed it and still no difference. I'm fairly certain I have...

Case 580C, 207D, backfire rough running