What cam to use in a 318

Furz4,
You have given this considerable thought....& your reasoning is excellent. The only incompatibility I see is 3.23 gears & a high stall c'ter. Not a big deal, but something to think about in the overall picture.
Refreshing also to see somebody thinking about the cam & not automatically installing Big Bertha.
I would use the Isky 270 Mega cam. I have used a lot of the Mega cams. The tight 108 LSA is going to give you more HP.
221 @ 050 might not sound that big, but it has 12* more overlap than the same grind on 114*. Single pattern, lift will be 0.496" with 1.6 rockers.

Remember, easy to go too big. Have factory lifters re-faced if you do NOT want lobe/lifter failure, no matter what brand the cam/lifters are.