Lets try this approach!..

[What's_nitro?]

Lifting body, anyone?

[Metallover]

maybe just a speed project...

If you want to go with the longest jumping truck, I'd do a simple 2wd with a pan-car type chassis modded to go offroad. You could get the massive speeds and have a lightweight car that would fly further.

For the ramp, 45* is the way to go. The only reason to change it would be to get it to fly better or land ok. 45* is the most efficient angle to launch anything.