Help me change my gearing
 

I recently acquired a mid nineties Marinoni Leggero. It has a 8-speed campagnolo cassette with 13-21T sprockets, and 39-53 chainrings. Given that I live in an area with lots of hills I want to switch to larger gears in the back. What are my options in order to keep both derailleurs (campagnolo record)? Can I simply switch some of the sprockets and add let's say a 23, and 26? What's the largest I can go with?

With my Chorus 9 speed, I have a 29 tooth rear cog. It shifts fine. You can simple change cogs to get what you want or buy a new cassette. You may also need a new chain.

many here use a campy nr rd with a 14-28t cluster.

on the safe side, you should certainly be able to shift it to a 26t cog with any hanger and wheel position.

I did that with my Trek 760. Removed the 13-26 and installed the 14-28. Easy schmeezy.