SS Slant Six Dart

If you have an old /6 Valve cover and you want to alter weight in your Dart, oil down the inside and fill it with concrete and put any kind of reinforcement in it, stick a couple pencils in each end some where so you can wallow out a hole to bolt it down, Don't use to much water and tamper/vibrate it let it set up pop it out and there you have it.
I bet you would be surprised how heavy a /6 solid concrete valve cover is.
This is an old dirt track trick