Which do you prefer on a stock 170? Carter or Holley 1920?

I don't know that any rod-throttle carb is easily available (what I think you have on 65 slant), though you might change to a 65 V-8 cable throttle to use later carbs. The Holley 1920 is great when it works, but too many have clogged metering blocks that aren't fixed when rebuilt. Some people know how to blow them out. The Carter BBS 1bbl is much simpler to rebuild correctly and adjust, since just like the extremely common BBD 2 bbl.