I used a 4x4 block of wood in the exhaust and a floor jack to add a little clearance, but alas, mine were SBC, sprint car headers, and were almost completely shot. It worked for the next several seasons.
Jet boat headers are approx 5* down, as as manufactured, and v-drive are approx 5* up as manufactured, a difference of 10* (approx), just an FYI.
Dan'l