you will still need to use the a-series gearbox yoke, most drive shaft builders will drill the yoke out and fit bigger replaceable unis, you definately need stronger uni's than standard for motorsport (front and back of shaft)

my guy would charge $200 to replace uni's, make a new shaft to length to suit and balance the whole unit, he is in fern tree gully melbourne, depending on where you are you should be able to find someone to do it for around that price