I have a 70s 400 that I don't know a lot about but it has adjustable rockers on it like came on hp 383 and I keep having problems with them coming loose (don't believe they are the correct parts)
and I got all new lifters, push rods ( after finding correct length I hope) new adjustment screws but in putting it back together it seems to tight I have the shortest push rods I can find and some are still loose but doesn't feel right for some reason. So my question is I have a set of stamped on another 400 from 77 can I just swap them on and not worry about the adjustment it's not a radical cam and hydraulic lifters but I don't know anything else .I am looking to have something I don't have to adjust every time I drive it thanks for any help you can give

 

Welcome.
With the mix of parts and uncertainty, I would look to a cam manufacturers pushrod length checking tool. You could set up one cylinder and use a dial indicator to check preload which would verify correct length but bolting it together on someones say so is not a risk I would be willing to take. Good luck with your project.