HydroBoost vent tube

I am installing a deep water fording kit. The kit is from ebay. I am working on the vent line from the hydroboost. Instructions call for elbow 12339964-1. I've searched the NSN and I have what appears to be that elbow but it is too large to fit the vent hole opening on the bottom of the hydroboost.
It is about impossible to see the vent opening so I ended up cutting in an access panel. No way that what I have is fitting the vent hole.

Can someone verify what size the fitting is supposed to be? Caliper says outside of the threads is about .4 inches on what I have.
I went to multiple places today trying to find some smaller fittings to try but didn't have any luck.
I am hesitant to tap the hole larger without getting some opinions first.

The tubing that came with the kit (3/8" OD brake line) is also too large for most of the barbed end on the fittings also.

My hmmwv is an 87 GP from Yermo California.

Thanks for any assistance or insight you might be able to provide.

It is a small elbow pipe thread. It is whatever is the next smallest down from 1/8. Real odd size. I found a chart that lists it as 1/16. Other side is a standard nipple slip on I think 1/4 hard nylon tubing like air brake line.

Thanks for the help and confirmation.
I'll order some 1/16 fittings since I couldn't find any locally.
I was able to confirm that my kit came with 1/8 fittings. It is hard enough to thread something you can't see and can barely touch, even more so with the wrong size fitting.
Thanks again.

kantucky said:

Thanks for the help and confirmation.
I'll order some 1/16 fittings since I couldn't find any locally.
I was able to confirm that my kit came with 1/8 fittings. It is hard enough to thread something you can't see and can barely touch, even more so with the wrong size fitting.
Thanks again.

Click to expand...

it requires you remove the splash shield on the left side....an approximate 15min job.