The Weiand may be a little tall for the Scamp's hood depending on the aircleaner.
My notes are the average pad height on the 8007 & 8022 is 5.41"
The LD340 is 5.12"
The Performer RPM is around 5.35

My opinion is the the LD4B is probably better for street than the LD340. If you stick with the LD4B after repairs, you could open up the ports a little to match the heads. I think the runners are smaller than the LD340 and will keep the velocity up better. The RPM's runners are definately smaller cross section. I have both the LD340 and the RPM but have not yet had a chance to try out the RPM. So like everyone else, its all theory, no back to back!