I thought the 89 318 was a roller block did you use a flat tapper cam over the roller for some reason? I think it will be some what a wash. Unless you added better pistons. Also, you’re talking about a truck so where do want the usable power down low right so the stock magnum probably wins in that regard. The magnum heads are better in stock form and have the 1.6 ratio. Any performance gained by the xe262 wouldn’t net much more than the better flowing magnum heads. I would love to see both motors tested and see what the results are.