No, no, no, you don't need a manual tranny!
If you buy a valve body from a 67-69 C-4, you'll have the conventional 1-2-D shift pattern. A rebuilt valve body from a trans shop is about $100. Buy a shift kit for about $70, and you're set to go.
I've done the valve body conversion, it could not be easier. The worst part is getting ATF all over your driveway, that's it.
Hope this helps