Could be a head gasket too. Had the same problem on my Fury after I did the magnum head swap. I got a bad MP gasket....so bad it would blow the dipstick out of the tube at anything over 1,500rpm. Switched to Fel-pro and it runs like a top

1969 Nova
454/M21/3.31
Mild mid-11 second weekend cruiser

1994 F150 XLT Super Cab 2WD
5.0/4R70W/3.55
(Daily driver)