As the title implies: looking for a quality fuel vapor separator for my 68 Hemi car. I remember a discussion a few years ago regarding the repop's at that time and the consensus was that they were not designed correctly and would lead to driveability issues. Have those issues been solved, or are there no good options?

Buy one from 521 Restorations. They have the correct ones.
https://521restorations.com

I got mine from mopar mall. The small nipple is the correct size of .060 and the huge one is the problem child.

https://www.forbbodiesonly.com/moparforum/threads/fuel-vapor-separator.236061/
Go to post #13.

As far as I know Frank Baldson is the only one that has them with a screen in it. But it doesn't have the correct orfice, so I just made a small plug and drilled the hole in it and slid it in the hose for the return line.

this is all great information. What is the driveability problems with using the repros?

Most didn't have a screen and as such not filter what so ever. With out the little orifice being .060 the fuel pressure can be to low.

In my experience.
Unless you consistantly hammer on it.
You may never know if it's wrong or right.
Normal around town drives. Odds are you'll never detect an issue

I went through pressure loss problems when I was setting up my 68 Hemi Runner. Even with the factory .060" return I had about 1.5-2 psi loss from when the line was clamped closed. I soldered the opening and with a little trial and error, I ended up with a .035"ish opening and with just a slight loss in pressure but still allowing enough flow to keep the function. I have had no issues in the past ten years or so with vapor lock but I also used a couple short pieces of insulation around the fuel line where it has close proximity to the exhaust pipe.
This may or may not work for you but keep in mind that you might need to make small modifications to enhance the OEM function.

68jim