I just fitted a worked A14 to my formerly "grandad spec" 310. And to be perfectly honest it feels slow. It sits there rumpity rumpy away at Idle, but after having driven the supercharged A14 fir two weeks it feels like an old womens car.
I am pretty much fed up with lumpy cams.
An Lseries would give smooth power without needing a cam that makes your fillings drop out of your head. But on the other hand, the "A" will be a cheaper way to go fast, If you don't mind a trade off for low end driving.
Sure, you may choose to go S/C option, but without some engineering skill, or a good matre with some it will get expensive quite fast.

Going off topic a wee bit, will a 180B Xmember bolt into a B310?