Brake Master Cylinder Outlet Fittings - What is Correct?

[DeathProofCuda]

I recently bought another parts store master cylinder for my Cuda due to a minor leaking issue with the previous one.  The previous one was a Raybestos MC36221 (Photo 1) from Rock Auto.  New one is a Centric 13063055, also from Rock Auto.  When I first inspected the new Centric MC, I noticed that the hole in the outlet port for the rear chamber was much larger than the front, and there doesn't appear to be a brass seat for the flare fitting to mate against (Photo 2).  Thinking this was odd, I compared it to the Raybestos MC, which appears to have similarly sized outlet holes in both ports.

I also checked it against another MC I have on the shelf MBM MC5621, which also has similarly sized outlet holes both front and back (Photo 3).

To me, the rear hole in the Centric MC looks so large that I can't imagine the inverted flare fitting ever sealing properly, so I made arrangements to return the Centric MC to Rock Auto and instead ordered another replacement from O'Reillys, Best Brake Select, NMC 11280.  The Best Brake MC actually appears to be made of aluminum instead of cast iron, and only weighs about 3.5 pounds, instead of 8+ pounds for the other MCs.  The Best Brake MC again has a larger outlet hole for the rear chamber and does not appear to have a brass fitting in the rear port like the Raybestos and MBM MCs do (Photo 4).

So am I correct in thinking that the Centric MC will leak like a sieve due to that large hole on the rear port, and will the lack of a brass fitting in the Brake Best MC also be an issue?

Also, any downsides to the Best Brake aluminum MC?  I kind of like the idea of a generally appearing original MC that won't rust without being painted.

[DeathProofCuda]

@JS27N0B

Thinking that you might be our authority on this issue???

[JH27N0B]

If you meant me, I used to work at the company that made Raybestos/NAPA United brake parts, and after doing a lot of research wrote an article in Mopar Action on identifying correct OEM Mopar master cylinders from the muscle car years.  I got laid off in 2005 when they started closing down North American manufacturing and moving it mostly to Asia. 
So I guess I could say I'm an authority on OEM Bendix manufactured master cylinders and back in the day aftermarket, but I have been out of that industry for almost 20 years now, and haven't got much knowledge of the current product offerings.
The pictures you showed all are a B/C body style disc brake master cylinder. Raybestos part was MC36283.  It's 1-1/8" bore, and the outlets off the top of my head I think are 1/2-20 and 9/16-18.  Which were standard outlet sizes for all the Mopar master cylinders back then.  The MK36221 part you cited is the 4 wheel drum brake MC across the board 67-70 models.  It had a 1" bore.  So I am wondering why Rock Auto was sending you a 1-1/8" disc brake MC instead of the the 1" drum brake one that part number is for?
https://www.classicindustries.com/product/all-years/dodge/w100/parts/MC36221.html?gad_source=1&gclid=EAIaIQobChMI0rPOg6DWhgMVvF9HAR1uJQ_oEAQYAyABEgL2tPD_BwE&gclsrc=aw.ds
They should have brass seats for proper sealing.  As far as I recall they always had the same size holes in them, only change I saw when I worked in that industry was they used to have residual pressure valves installed under the seats to help prevent seepage from the wheel cylinders when at rest, and those were phased out with new spring and seal design in wheel cylinders to stop the seepage.
I have disc brake E bodies and have used the B body MC on a car before and it worked OK, but I thought the brakes a bit grabby compared to the OEM 1" rare and valuable OEM 2229171 for my '70s.  My '71 has a 1-1/32" MC correct for starting that year.  It works fine too.  There was/is an OEM equivalent MC36307 for that one.  I'd use one of those before a 1-18" bore MC if I was looking for an aftermarket MC for a disc brake E body.  I'd buy a correct MC36221 for a drum brake 70. 
Again, I've been out of the industry for almost 20 years so have no knowledge of current manufacturers or any design changes they've made.  It's all China junk in my mind and I miss the "good old days" when my work put out a great quality product made here in the USA.  Current product might be decent quality despite being made overseas, I just don't know.
People on forums talk about Dr Diff/Cass, as being an expert supplier of brake products and performance.  For someone familiar with current products for advice, I'd try to track down him if you need more info.
https://www.doctordiff.com/

[DeathProofCuda]

@JH27N0B

Apparently I can't get my numbers correct, both when trying to tag you and when referring to the part number for the Raybestos MC.

Thanks for your input and for confirming my suspicions that both of my new MCs are missing brass seats in the rear ports.