Conversion makes me think of Rustler, except with a different mechanic and theme. I like it.
I don't think you need to raise the cost by 1 for the upgrade though - considering that this "produces" less than Rustler overall (Rustler require 1
-> 2
. This requires 1
+ 1 card -> 2
at least), you could possibly lower the cost to 3 | 2 and make the unupped generate
as well, unless there'd some gamebreaker deck that I didn't think of.