Fort and I tried to figure out once why they had such a cockamamie design for their manifold, but I don't remember exactly what we figured it was. If I remember correctly, their manifold is designed to hook into the first needle valve before splitting into the two subsequent needle valves, but assuming you can remove the original needle valve, you should be able to put on any post body you want.
Edit: as far as using a bubble counter goes, I would still use it. For one, can you directly hook a co2 line into a needle valve? I've never tried it. Aside from that, a bubble counter is the only way you have to actually measure your output. It's worth $20 in my book to be able to actually measure your output. Aside from that, I would certainly feel like a fool if I had a $100+ probe system fail and end up having tank problems because I didn't have a cheap fallback part. It's not often that you can have a cheap and effective fallback system like you potentially have the opportunity to have here.