Whatever you do, don't lose the original 65 gearset with its 3.09 low gear. With street rear gears, the difference between the 3.09 and the 2.66 will amaze you. But not in a good way.
BTW, those 65 gears will fit in a later trans. That's what I have, after driving for a couple of years with a later trans and its original 2.66 low gear. With that trans and 3.23 rear gears, it was an absolute dog off the line. Fortunately, I saved the original 65 gears and they are what's in the car now.
