I have a 69 block 408w, with avenger R heads. It is in a ranger I have ran a best 6.49 105 mph, but since then put 5.14, new slicks, and went to allky. The guy that done my carb said to use cometic gaskets. Then I read a lot of people dont like MLS gaskets. That they are prone to leak and have to have perfect surface area. Some said to use 993 pt-1 but jegs and summit says they are for stock or street applications. I believe my block is ringed it has a wire around the cylinders that sticks up some. I had copper ones before but they started leaking.