I recently dropped a 460 in my 58 edsel. the engine came from a 78 E350 motorhome. I have a noise on the top end I think its lifters tapping at 55-60 mph and when im on it. After I let off from a high speed I can here one maybe two lifters that are empty. But heres what gets me I start to drive slower or if I pullover for a few minutes they fill back up then sounds fine at low speeds. Im not sure if i need lifters or the oil pump I put in isn't right. So this is what I did to engine before I dropped it in, new front sump oil pan, melling high volume oil pump, and cloyes double roller timing chain. I have been looking around on other forums but im not sure whats causing this issue.