If I was to build a 3k 318, I'd be expecting 375 gross hp minimum. That would be my expectation. Just for funs off the top of my head, something like this parts list:
Promaxx heads -1400 fully assembled
maybe something like the lunati 702 cam kit - 240
edelbrock timing set - 75
KB167 standard bore pistons/rings - 390
Full gasket kit - 70
used RPM intake - 200
If the engine ran good, I'd most likely re-use the bearings and oil pump
750 carb - 450
I have change left over....... You'd be pressed to buy and build a 340 to run with my combo.....