I agree 360 heads seems like a step backwards but trust me it makes up for it breathing mid and top end. 1.88-1.60 valves are much more 318 friendly than the 2.02-1.60 x heads when swapping them on a 318.

another trick is to up the 1.50 318 head exhaust valve for the 1.60 valves. I did a set of #302 heads with 1.88-1.60 valves but IMHO it needed a better porting job and flow bench to get them to full potential.

yea just clean up the ports a little, open the bowls up and see if they back cut the valves. I do some back cut on the valve with a bench drill press and a file when home porting but to have the shop do it on a valve machine is awesome and well worth the bang it gives.

tip** use some duct tap on the valve seat when grinding the bowls open in case you slip with stone or cutter. help dull the mistake when it happens.