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The 9425-B intake is dual plane from the factory. What did you do to it?
The cam will be a bad choice for a street engine. The Mutha thumpr is a bad choice in general because it is all about the sound so you are going to sacrifice power for sound and that is on top of the really big duration @.050"numbers which make it a bad choice for the street by themselves. There are plenty of well designed cams that will give you a performance sound, along with the performance. Mummert is a good source, www.ford-y-block.com. Isky cams is another. The best option is always to call your favorite cam grinder, answer their questions realistically and honestly and take what they give you.
Unless you have domed pistons, your compression is not 9.8:1. It will be about 9:1 at best, which will really be too low for a cam like that. That is another reason not to use it.
I think a more appropriate cam would be something with low to mid 230s @ .050" at the most. Even with a cam like that, don't plan to use the truck as a truck. You will be able to do light duty stuff but it will not have the low end to haul or tow like it was originally intended. Once the engine is built save for an aftermarket aluminum intake and higher ratio rocker arms as these will help you much more, for street performance, than a bigger cam. Dual exhaust of some kind, will also be needed. Headers are best but rams horns are an excellent choice for oem appearance.
If the heads have not been ported, then the most you can hope for is about 300hp.
Lawrenceville, GA