respline axles and chop the tubes

So i have the age old dilema of too wide of a rear end. i'm running the 74 dart that i have pictured in my avatar with...a stock width b body rear end out of a 66 charger. i already have 5.5 inches of backspacing, and after installing a 8 inch race ATI converter, i'm thinking that the 9 inches of MTT et street tread i have at the rear may not cut it. (bracket raced every weekend) the motor is a 408 with 480 some ft lbs of torque. there is ZERO room to come outward on the rims. but before fully understanding my geometry several years ago, i did a spring relocation giving me the inward space i need for alot bigger tires.

here's my question:
what is my best/cheapest/ most resourceful way to get more tire under the car.

first i was considering getting the tubes cut, and getting my stock axles resplined (since i already have press on green bearings installed)

this would allow me to use the parts i have, including the wheels (which were also a pretty penny,weld draglites)

some might point in the direction, of buying stock A body length axles and just cutting the tubes, but again thats more $ for bearing pressed on again, and then i am stuck with my old axles.

a buddy who is more...modern muscle than old school, pointed out the idea that he has had aluminum wheels cut, and had a piece added...this seems rather smart considering my outward spacing would not change, but they could add almost 4 inches inward worth of rim...may be more cost effective than all the narrowing and spline work.

whats everyones opinion? i'd really like to reuse as much as possible since i bought it once already!
any better ideas?
anyone know where in the OH area to get tubes cut and axles resplined or the wheels done?

thanks guys!!