318 combo

Running Propane with low compression and a rumpity-rump cam, i'm not surprised it's soft on the bottom end. Bet you need to run a lot of timing to get her going.

I can't really recommend a combo, since I really don't know how much your propane can take. Meaning what octane rating and if there's a certain amount of butane mix. Trying to keep the cylinder pressure up may call for talking to someone familiar with that type fuel on the camshaft choice.

Good Luck & i'll be watching :thumleft:.