Some of this got my curiousity and I took a measurement of the 6903 input. Here is a 6903 at the top and a hemi 4024 at bottom. These are period parts. 70s maybe early 80s, carter parts. Again, the 4862 and 6903 share all the same casting part numbers so the bodies are the same. The hemi is on the bottom, the parts are aligned with the smile matched. Bottom and middle only go together one way.
Notice the increased volume of the hemi body because of the gear shaped cavity. That is the output chamber that fuel is drawn into via the diaphragm. 2 valve for inlet, and single valve for outlet. Also notice how small the volume is on the outlet check valve slots.

On the bottom piece you can see how the hemi has an open inlet chamber immediately at the 1/4" NPT threaded hole. The 6903/4862 have a reduced transfer port that moves the inlet fuel to the opposite side. I measure this, and it is not 1/4". It actually is a 5/16" hole. So the 1/4" NPT input goes down to a .3125" hole, still larger than the 3/8" pipe ID even if slightly greater than .300".

Now maybe the newest stuff has smaller holes and such, but still the smallest restrictions are on the output side anyway.

So personnaly I would not be opening a new pump to modify it for a mild car; and if you had a more radical car and need more volume I would look for a 4024, or even some of the older Marine RB pumps that used the same chamber as the hemi. The few holley and such that I have opened still had this smaller chamber. Which is a reduction in volume per stroke, but also generates a slightly higher pressure at shut off to hold the spring compressed. But still plenty of fuel for most needs.

Thank You sir !
i kind of expected this was what was needed, and what was done to remedy the problem, but wanted confirmation of such.
Thank You again for your reply !

if the pumps share the same casting numbers, would it be possible the gear shaped cavity be in the newer pumps ?
the only way to know would be to open them up.
just asking in order to gain knowledge of the 6903 and 4024 pumps.
sorry if i sound so dumm................

6903 and 4862 share same casting. The 4024 is different, but some older style 60 pumps did share casting numbers with 4024. Yes casting numbers are inside. Only outside casting number is on the top arm assembly. Which despite different casting numbers I have not really found any significant difference. Same lever # and assembly. Vent varied some, but.....

I have ran Carters, Edelbrocks, Clay Smith, a Race Pump and a few other auto parts brands. You have to be careful with the PSI ratings they are all over the place.

IMO an Aeromotive Stealth tank is the hot setup for anything that need more than a stock style mechanical pump. There are very few applications I could see the Clay Smith or Race Pump being logical.

Hence why the Race Pump is on the sheld and nobody will buy it LOL.