I agree with all the guys above, I swapped a 454 for a 350 in a '74 Suburban, bolt-in deal. I had the complete 350 setup, brackets and all. Did it in -20 deg outside, got the burns on my arms from where I froze to the frame several times.
That Suburban was bought new and from day one there was a lifter noise. It went back to the dealer several times, they're conclusion - that's the way they are. I never tore the engine down, it ran fine until I pulled it for the guy. He was hard of hearing, never bothered him!