If you see valve marks on the tops of the pistons, you may very well have bent a valve. Any contact will do that. Since you have the head off, flip it up so the intake/Exhaust ports are facing straight up. Pour some solvent, mineral spirits or the like into each of the intake ports and see if you have any leaking into the combustion chamber. If you do, the head of he valve is tweaked. But you could also have a bent stem.
As for dual carbs, as Patrick Swaize said in the movie Roadhouse, "opinions vary". I love them and have run them for close to 40 years. All kinds. Some run better then others. I like the 1974 Ford pinto holley weber 5200 progressive two bbl for a 2X2 set up. You can use adapters on a vintage intake, that set up runs really well, out of the box. I think the smaller carter/webers that Tom Langdon sells are also a decent choice for a 235. If you want new carbs, not rebuild, then use the weber 32/36 carbs instead of the pinto carbs.
I ran the dual pinto set up on an old Weiand manifold on a 235 for 20 years. Put it on a 261 motor and it ran equally well. I recently switched over to a Clifford 2X2 and that intake is a pretty nice piece. Give me a moment and I will post a photo of the Weiand pinto carb set up.
