Bill, since you are looking to put your car on a diet, have you looked at your battery combo; ie do you have a 16 or 24 volt battery on the car to start and run your transbrake, computer, rear light ? If so, you can save more weight by changing you battery combo than lighter axles. The biggest savings would be if you carry 16-24 volt batteries to start your car. You could change to a remote battery pack for starting. However if you want an on board battery because you worry about the motor dying on the burn-out or you have limited crew, you could install lighter battery in the front of your car and remove equal amount of ballast. If you already use a remote battery pack for starting but still have a battery on board to run the rest of your electronics [ ie transbrake, RPM / RacePak] any battery that weighs more than one pound, you can save that weight also. Start by weighing your batteries to see what you can save. We saved 6 lbs by switching to a light lith battery [ one lb] to run our transbrake, and RacePak] We also switched to two 12 volt 500 cc amp batts that weigh under 9 lbs, to start the high compression motor.
And/ Or you could spend $1000-$2000 to take 30-40 lbs off your iron block.
Also take a real good look at your racecar looking at every bracket, mount, nut and bolt, puke tank and hoses, rear wheels, size/ weight of your chute, wheelie bar to see what you can remove or modify to remove weight you don't need.
Good luck finding parts to remove, remember, it all adds up, lots of 1/2 lb reductions adds up to your 150 lb weight reduction goal.
Jon , 805-444-4489