Had a similar combo in my dart:
- low CR 360 smog motor (~7.8:1 when I pulled it apart)
- Smog heads, 1.88/1.60 valves, no port work.
- Cast iron 340 manifold/600 holley
- Summit .441/.441 with 218/228 @ 0.050
- Hooker 1 5/8 headers
- 999 trans with stock lock-up converter
- 3.23's

Ran best on 87, and ran 14.0's, but I forget the MPH. Real street friendly motor. This was a year round daily driver through the Northeast snow...

Spun a bearing in that and through together another 360:
- H116cp slugs
- XE268H cam
- ported J heads
- LD340, 750 holley

ran consistent 12.80's at 107, but a bit less bottom end.

Headers would help for sure. Like Greg said, thin head gasket, block the heat crossover.