budget street motor 360 or 383 for 71 duster

Ok so sounds like the 360 is the way to go only reason I was asking was I did get a couple quotes when i thought i neededmore power to beat him and they were in the range of 11 to 13k for a 550hp roller motor thats what made me think go big block but now im little more reserved and just want to have more fun and beat up on some chevys haha. Would my 360be the way to go or use a magnum motor thinking I'll use some aluminum heads incase I want to go bigger down the road. The thought of having a big block in there tho is a cool idea.