Backpressure is not good. I'm not going to get into a whole essay on exhaust velocity and scavenging, but in your case, HP manifolds are better than log manifolds and headers are a step better yet.
Until you pull a cylinder head off and measure how far down in the hole your pistons are, as well as any dish or valve reliefs, we are guessing at your compression ratio, which isn't a good way to pick a cam.
Okay, I will look around for something better than the truck manifolds I have then
Unfortunately, I don't have room to take the motor out until I have finished other projects. I will not order the cam until I get the heads off like you say, I need to do all the measurements before, but I need to find an intake before that.
