"I" should look into making a casting? Why don't you want to do it?
Casting has already been covered ten different ways. I wouldn't mind a friendly discussion about casted parts, but truely, casting for short run complex parts(less than 1-2000) are three times the cost as making them out of billet. With billet parts, anything can be changed on the fly.
Core dimesions always change with castings and those problems only get worse as the casting tooling ages, you are releying on people to assemble to cores correctly, when the castings cool they distort. Casting problems just go on and on. I am over it.
I know when I take parts out of the machine the dimensions are dead nuts, everytime. I don't have to rely on someone else to get me the castings on time and making me look bad in the process. I can place a call and the material I need is here within three days.
When you are done machining a casting, they just look like cast parts machined to look pretty.
Enough of that,
Let's see some pictures of your case. Looks like it is setup for a GPR cylinder.
Brian
I too have machined a set of billet crankcases. it is alot of work getting it setup. You should look into making sand cast cases or perm mold. Make the transfer area blank and machine it for whatever cyl you want. You will find that the cases weigh alot more machining them from billet. Once you make the tooling for casting you will be able to make quite a few for very little $$.