273 2bbl turn into Commando or is 318 better?

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I've just bought this 1967 Dodge ute with /6 and 3 speed manual.
I may have the oportunity to buy a 273 2bbl and auto which was an option on these. We never got the Commando version here but they sound interesting. What would be needed to upgrade a 2bbl version to Commando spec's? Would that be a worth while option or do you think a 318 would be better or just more cost efficant? This is to be a daily driver.
Your opinion would be helpful!