Clutch kit recommendation needed

Diaphragm clutchs are the easiest to depress and hold, for the same clamp-pressure.
If you install a 9.5, you better put a 2bbl on that 340,lol.
The thing is that on a 4-bbl carb, the primaries and secondaries have to reach WOT simultaneously. That means, the Primaries start opening the Secondaries at somewhere around 50% of the Primary throttle opening. Now; the Factory 340 was never known for a strong bottom end, so you may be driving deeper into the throttle than you think. Just something to keep in mind if you keep the 9.5.

The thing is, if your 340 is a low compression model, you can really increase the low-rpm grunt with a shorter-period cam. I once, in the 70s, installed a complete 318 top end and cam, onto a 340, which made it a torque-monster. It made short work of the 904 behind it, which was originally behind a 273, lol. Hey, I was a broke-azz 22 year old with no job; I just threw together what was available, for cheap or barter.