I agree. Its a bit like finding a NOS RM125S bore or a Noguchi.
Modern tech applied to any domestic part will out perform period factory performance parts every time. But as a collector/restorer, to preserve something you have a passion for, that is something the individual has to value and isnt that what many of us do by playing with old machines? What its actually worth is only what someone is willing to pay for it despite the actual performance.
What makes it unique besides the porting is its cast with the numbers 173 not 183 and that makes it a rare item indeed to the 185aholic , quite desirable.