Kevin,
I'm no expert in this one, and suspect you are looking way above 1/2A on this. The spray bar has no needle. Even any of the bigger conversions the needle is remote, and the spray bar is modified to no longer need the needle...either by blanking off the end, or by plugging the fuel nipple and running the line to where the needle once was. Or, in the case of OS, a replacement spray bar with only an inlet and hole/outlet replaces the more traditional needle/spray bar.

I read that some will solder an outlet onto a spray bar with soldered-on bracket to create a remote needle valve, and then place a "needle-less" spray bar in the venturi...either custom built as inlet/outlet, or, again, blanked-off where the needle used to be.
I sure hope all that makes sense...it is the best I can come up with in a blink. I wish I kept those links now!

I see Dub Jett makes some pretty cool remote NVA's and the OS  are ones are hard to F
find. My question is you will now have 2 NVA's, the remote one and the one in the venturi. How the heck does that work??

The one on the left is what Nelson used on his RV 15's.

Thanks for the feedback gentleman. The engine in question is the Fox 36 VI. Basically I can just use an old needle valve and block off the end.