the drilled fitting is for a vent, normal on endurance trans

 

Thanks for the info on the vent, I am looking for info on the fill plug on the driver side of the case behind the bellhousing

 

If I had to guess, I'd say maybe what you think is a fill plug is actually a return hole for a trans oil cooler maybe?? Just plugged because the trans isn't installed and ready to run right now?
The location would serve to put the oil right at the input gear to cluster gear interface and close to the input bearing for both oiling and cooling.

The 2.43, 1.61, and 1.23 stampings are the 1st, 2nd, and 3rd gear ratio's.

 

It looks pretty good, as Eric said, may have had a fluid cooler to it. I dont like the generic cast iron shift forks, there are american made STEEL ones out there on the market. But thats a personal thing
I doubt DNA is Doug Nash related but who knows.
lmsport mentioned a vent, its imperitive you run a vent on a T10 made after about 1963.
32-spline outputs in mid 50s cars n trucks can be a bit of an adventure. Its the TH400 length driveshaft and slipyoke, and you've lost the foreward-most shifter mount. Eric @ Crash Enterprises (crashenterprises.net) can hook you up for the best quality stuff. I have to say the quality of the modern "Hurst" shifter kit is pretty hit-and-miss.

For basic gear oil, you want something with the correct synchro additives, 90% of the stuff on the shelves these days due to the rising cost of oil is now regulated to "not for synchronized transmissions".

Here's the stuff we have the best luck with as of today:
Driven Racing Oil (under the comp cams umbrella) 80w90 P/N 04530
Royal Purple "Max Gear" (only) 75w90 P/N 01300
AMSoil Manual Transmission Transaxle and Gear Lube 75w90 P/N MTGPK
RedLine 75W90NS (specifically the NS)

Most of these mention T10s Toploaders and Muncies right on the back label. Theyre all safe for yellow metals, and have loads of synchro compounds and a good bit of rust inhibitors. Yes there are others that may or may not work, but as of today, this is the current list we provide with gearboxes under warranty.

Driven is probably the best for older builds/looser tolerances or unknown quality synchros. RP Max Gear is in just about every auto parts store. I've even seen it at Walmart occasionally.

 

Thank you for the information! The plug in question is wire wrapped to the case, and has IN written with what looks like a sharpie or grease pencil above it.

As for the serial number stamped on the case, I was thinking DN was Doug Nash. I was told in a classic 4 speed group that Doug Nash had a factory that re-furbished these units in the 80's before it was sold to Richmond. I don't know if that is accurate or not, I cannot find any info related to the stamp. This trans sat on a shelf in the back of an old transmission shop here in Florida for many years. I am assuming that this unit was prepped for circle track racing, most of the hardware has holes for wire wrapping.

I have a mildly built LS that I have it mated to, billet flywheel with a centerforce dual friction clutch. It's mocked up in the picture below, I am still waiting on the proper hardware and shifter. It'll likely be dropped in this weekend.

 

needs bigger tires

 

Looks great. DNE was a big deal for a long time. Doug was friends with my boss and they assisted each other several times. Doug did buy the ST10 tooling/line from Warner. It was hopelessly wore out, so what started with "how much money do you want to turn it on" quickly led to Doug getting a purchase order agreement from GM, getting a bank loan, buying the required bits from BW and then setting up his own plant. Talk about insane.
I don't know if the A prefix was used to signify a reman/refurbished DNE 4spd. However, (this is where I irritate people sometimes) even IF thats a DN code, the only thing that signifies at this point is that the aluminum housing was stamped by someone, somewhere with that string of digits. Theres absolutely no guarantee that the parts installed as of today, were the parts indicated, or even if they were installed when the case was stamped.
Trust but verify.

I see this a LOT with Muncie restorations. Every Muncie is a rockcrusher when you buy em on the 'bay or craigs.

2.64 1st would be great for an axle between 3.36-3.73. If you went with a 28" tall tire, I'd want 3.42-3.73s

 

Thanks for the information, and cool story! It is very unlikely that I will find any documentation on the origin of the serial number, just thought I would reach out here and see if there were any old salts that would have a clue as to what this thing is.

Here is what I have for passenger side casting numbers.

 

I don't see a thrust flange between 2nd and 3rd, which is kind of weird because it has a fine-spline input.

Can you post the casting numbers? Psgr side, wither WG Div or 1304-xxx

 

Last thing and then I'll go away.
You NEED to check that installed bellhousing for concentricity with the pilot bore in the crank. And you SHOULD check the back face of the bellhousing for parallelism with the flywheel

 

The full engine / trans assembled picture....looks like you are missing the block plate between engine and bellhousing??