Just to give you the way it is in the real world on horsepower for your car.
1. new car bought from dealer ship, say 350 hp, cost of mod per hp is 100lbs of weight off the car. or $100.00 that is for the first 20 hp.
then it changes to 300lbs or $500.00 per hp for the next 20 or so hp
by now your 1/4 mile time has gone from 14.10 to 12.99,
now you don't look at hp any more you look at lowering your ET so now you need to spend $1000.00 to $2000.000 to drop you by a tenth, so cost of the car + your mods and maybe you can run 12.00 or 11.90 .
2. you buy a so called race car ready for the track but want more say like a GTR cost $112,000 ,claimed 480hp runs in the 11's add $100,000.00 and run in the low 9's so that is $2600.00 per tenth. this was a friend of mine and it is facts. he did it because the first time he ran me he lost,,,didn't see him for 6 months , then he shows up at the track and said jim i want to run you again, i ran a 10.74, he ran a 9.32
3. now is the time for a V8 for a lot less money.
USAF 1964 to 1968 jim
also see the GTR's hp here
Larry Webster: What is the GT-R's Real Horsepower? - Column - Car and Driver