Hi, You are a clever man.
The exhaust port is the one that needs all the work.
You need to spend alot of time in there, standard valves are ok.
You can get 155 cfm from the exhaust port on an N42, no welding just lots of porting.
I do have pictures but i like to protect the work i do on my customers engines for them.
I am more than willing to port a cylinder head for you.