Building a 340

Looks like an XE268H cam in it. Whatever bigger cam you choose will likely require different and dual springs.

I hope your rod caps are marked with the rod itself. Shouldn't do what you did. Take one rod out, put the cap on it with the nuts. No chance of mismatching them.

That one cylinder is really clean, popped a head gasket?

Might do a quick hone/fresh rings and put it back together.

All depends on how fat the wallet is on where you go with the process.
It had a flat Tappet cam in it that I already thought I wanted to go bigger than what it was.
The caps were all numbered, looking back, I agree, better practice for rebuilding.
The motor had been sitting for a while, not sure last run, but there was a piston rusted down in the piston with no flex as the ring should.
Happy to be going through the steps