Curious as to why you think moving the motor back is the right thing to do. We have no idea what the weight percentages are on the car and THAT is what matters, NOT where the motor sits. Automatically thinking the motor needs to sit under the windshield to make the car work is very old school thinking and most of the time is not needed to make a car work correctly. Tires, tracks and suspensions are much better these days, and cars needing to be 50/50 to work is not current thinking.

I know a lot depends on the performance level and intended usage, but MORE power, directly equates usually to the car needing MORE nose weight. We have to run our drag radial car at better than 55% on the nose, or it wants to turn over. I was recently working on an older type top sportsman car that was 52% on the nose, with an 800+ nitrous motor that we were NEVER able to hit hard enough to get it on the tire.

I know those are extreme examples, but the OP DOES have a large HEMI with a blower. Common sense would tell you it makes tons of torque. That is going to punish the tire and suspension. The motor too far back will only increase that fact.

But to the original premise of the post, lost weight is FREE horsepower, and the more weight you lose, the more power you make. So 10-15lbs is 10-15lbs