Overdrive and underdrive pulley systems are available from RARE in Billet Aluminum if you really don't care about original.
...not for the '68 and earlier 8 bolts. I looked high and low. You have to switch over to the 11 bolt timing cover/waterpump if you want to use the billet stuff.
It seems most use the 11 bolt covers anymore. KRE just came out with a replacement 8 bolt cover within the last year or so. $175!!!
I'm a hobbyist. Not a professional. Don't be hatin'!