I have used the felpro gasket on a few slants. never had an issue. just make sure you follow the torque spec. if I remember correctly it is really low, like 10ft lbs.
And following the torque spec is true when using the stock one piece cast iron exhaust. The one piece cast exhaust manifold needs to have the ability to expand and move.
When I used cast iron dual Dutra's and the steel two piece Hooker long tube headers and this would also apply to the steel Clifford two piece headers, I tightened the mounting bolts pretty tight with no bad effects. I was using my 1/4 inch drive socket set, so I did not get huge torque, but I was more than 10 ft lbs.
