Master Cylinder Mounting stud loose

[High School 69 Charger]

I am replacing my Master Cylinder on a 69 Dodge Charger.  4 wheel Drum Manual Brake system.    The new Master i just got from NAPA looks great BUT the "ribbed" studs that should press in for mounting just spin.  The wholes on the Master are the outside diameter of the "ribbed" Studs.   There is another post on this forum where a guy showed the studs and talked about them being a press fit.  This is exactly how I removed them from the old Master.   Napa has ordered a second (but same part number Part #: NMC M1874M) and I also have a unit ordered from O'Reilly.   I am really hoping one of them matches and the stud fits as a press in.   I also tried AutoZone.  They had one on hand and it was the same problem but I'm pretty sure the one they had was for front Discs because the plugs on the Front and Rear Output ports were different.  And its' my understanding they are only different on Disc/Drum due to the Residual valve only used on Drum.
Does anyone have a similar experience or solution?

Here is a link to the other topic that has a pic of the studs in case anyone needs to check.
http://www.dodgecharger.com/forum/index.php/topic,70877.0.html

[472 R/T SE]

Do you have pix of both masters?

[High School 69 Charger]

I already returned the NAPA but the attachment should be my current.

[High School 69 Charger]

Here is a screen shot of the pic which might fix the resolution limit and distortion from previous pic.

[High School 69 Charger]

and here is the link to the napa part:
https://www.napaonline.com/en/p/NMCM1874M?impressionRank=2
and a screenshot.
Its simply the holes are a larger diameter for mounting so the "ribbed" studs simply spin.
Thanks for any help,
Martin

[472 R/T SE]

If it was a manual disc cylinder, the rear port would be bigger for more fluid. 
Both ports small and same size...manual drum.

[High School 69 Charger]

so that confirms my current is manual and drum (which is correct) but doesn't explain why the new NAPA replacement has holes bored out so the studs don't lock so you can't install it.    I know i did this before with this one but was easily 10plus years ago.    So I have the right current master cyclinder and it wasn't some previous error or shop switch.   Now I'm just looking for a current replacement that works.  i haven't seen anything on the forums of anyone running into a replacement that you can't put in the studs for mounting.   Hoping the 2nd replacement from NAPA or the O'Reilly unit is normal size holes and the studs will lock in.
BTW, none of the NAPA pics from their site show the Master open so can't really confirm the size and type.   And I already sent it back but when I go to check the new units I will look for that.
Thanks,
Martin

[b5blue]

Just Vice Grip each stud head while tightening. (I been down the road you're on.)

[High School 69 Charger]

Thanks so much for the confirmation that this happens with some of the current "replacement" units.   You really start doubting yourself (what am I doing wrong) so a simple response of been there done that is very reassuring.   I am hoping the O'Reilly brand might have the correct dimensions but now from your response I know if it doesn't just move on and go forward.   
Very appreciated @b5blue.
And thanks @472 R/T SE for the information on identifying the Master Cylinder types.
I will try to remember to post back on what I find if one brand seems to be correct vs the other.   Almost all of them appear to be in $40-50 range and origin in China so I have not really seen much difference there.
Thanks again,
Martin

[John_Kunkel]

Just Vice Grip each stud head while tightening. (I been down the road you're on.)

Or epoxy the studs in place.

[High School 69 Charger]

Well both the NAPA and O'Reilly Master Cylinders have the larger diameter mounting holes.   I went forward using the epoxy and vice grip tips offered and finished the mounting without too much problem.
I then found that both of my fittings didn't seat well.   They got very tight before seating the tube on the flare.   I thought i was going to have to cut the flare and change the fitting when I found the new fitting was also tight (actually an adapter and new standard fitting as 9/16-20 not available).  Once i knew it was just tight, I started walking the original fittings into the master Cylinder.  3/8 turn forward and 1/4 back.  Then repeat which walks it forward about 1.8 at a time.   I got about two more revolutions and finally the tube seated.   It worked but i was sure worried about it getting stuck.   I expect the threads are not cut clean plus they coat it for protection and this just makes it all very tight.
End of the day (hours later), I finally had my master Cylinder replaced and bled all the brakes (bled the master cylinder on the bench).
Thanks to all,
Martin

[b5blue]

 

[472 R/T SE]

I have 100s of pictures thru the years. This ol Vista computer is harder than hell to work with to get the pix out of it, smh.  I can't get updates.
When we did the master, booster on AllBlueRT, a buddy picked the master up for me and it was the one they give you.  I had to order the "correct" one.

Bendix, etc. boosters, masters and how the owners restore them has been a pet peeve of mine, lol.
Bendix's were painted as a whole unit so the master & booster, studs, nuts are supposed to be black.  Not a black Bendix & natural master.

We're gonna need pix, lol.