hehe, at this point, I've offered an answer to this one so many times I just went and took a new picture just for this time. I really need to write this up and make it part of the electrical sticky, then I could just send a link.
Note that this was not my creation, but rather an answer offered to me by other members here, particularly CarlC, who has a good writeup of this on his website.
You are in good shape to do this, since you have the correct setup for a 68, but have a newer engine which will have the accesory boltholes on the front of the heads.
So, without further ado (adu?) here we go again:
The brackets they give you for drivers side alternator mounting with headers are awful. They move around, throw belts, and crack. In 69, Chevy went to pass side mounting with way better bracketry, those of us who have 67-68's & headers had to come up with something better.
Corvette's stayed with short pumps and drivers side alternators until 1982. They used a big solid bracket that bolts to the front of the head. Earlier cars used an iron bracket, later years used alluminum. Here's a pic of my 1978 covrvette alluminum bracket, after a good polish job. The adjusting strap is an off the shelf item at autozone, I used the second of the 2 holes that were in it. The stud attaching it is a standard vette part for this setup.
I originally bought it from one of the corvette repro houses. I later found that gmpartsdirect.com sells it for half the price. Sorry, I don't have the part number, but any Chevy dealer can look it up for you, maybe someone who knows will post up.