I've made a few intakes. You definitely need heads and block to get it right if anything is not standard. Aluminum moves around a lot when welding. The intake needs to start off bigger than needed, then finished to fit.
I am not soliciting work here. this kind of stuff is a hobby for me. The intake in these pics cost less than $140 including the home built throttle bodies. It would have been more expensive to buy a cast intake, not to mention that the ports were raised beyond any standard offering.