'75 360 Rebuild, Cam?
How much does the porting cost?
I can not answer that because porting costs vari machine shop to machine shop, state to state, region to region, but, I can offer a solution. You’ll just have to add the cost of shipping your heads there and back unless you can drive there for fun and write off the costs as vacation..... LMAO!
Shady Dell Speed Shop
Or
Modern cylinder head
Both have excellent CNC programs.
Check around your area for a good recommendation and ask the machinist for price quotes and ask what specifically is done to the head and what you should expect back. Have a good chat with the machinist. Tell him your new to this. Speak with him like he is your buddy and you should be just fine.
Everybody is in the same area for cost vs work done and end results.