#1
The port configuration at the base of the cylinder has been updated slightly, without seeing your cases, I am guessing they would be close, but probably will need a little bit of work to match the billet cylinder perfectly.
#2
At the smaller bore sizes, ie.. not the big bore cylinder, the power gains over a cast Lamey will be minimal, it is a replacement to the cast Lamey made out of a much better material. It is a much better part all around, right out of the box.
Is it worth it to switch from a cast Lamey to a billet Lamey? Depends on why you are asking I guess. I can address your specific concerns if you do want to do the switch. But I think the short answer is no, the cylinder you have will serve you just fine until you are ready for a big bore cylinder.
Brian