new lifter ?

Good idea to check the cam before going any further. You should be able to get a good view by removing the intake as a first step. If the cam is good you can install new lifters on a used cam. Break in the new lifters if you change them.

When you selected your new pushrods, did you measure for the correct length? Your rocker arm adjusters should have 1 to 2 threads showing only with the right preload set. When installing the pushrods are you sure you adjusted the rockers appropriately with the cam on the base circle, adjust to 0 lash and then add 1/2 to one turn on the adjuster to set the hydraulic lifter preload? On hydraulic lifters with adjustable rockers I usually measure, with the intake off, the amount of preload with a wire feeler gauge between the plunger and snap ring on the lifter. I measure the distance to get the recommended amount of minimum clearance and count how many turns of the adjuster it took to achieve it from 0 lash. I then set the rest without having to measure the snap ring clearance each time.