You're better off just going with new oil thru pushrods and oiling the top end that way. Just be sure your lifters have the oil hole on top. That Magnum block/LA top end oiling is a very difficult deal to get done. The passage must be exactly placed and it's like 6" long. If they are off even 2-3° in any direction you will not line up with the cam bearing hole.
I should add this is how a lot of high rpm race engines are done because it lets more oil be diverted to the lower end.