These guys make a great looking, performing product. I run one of their 4" aluminum Accu-bond 7075 driveshafts in my 1968.

https://www.markwilliams.com/aluminum-driveshafts.html

1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)