1 hour ago, tetert1 said:

How would you recommend unplugging the return line.. steam it out add chemicals? Try maybe pressure washing ,maybe a radiator shop might help? Small  drill bit?

I would start with compressed air. Maybe some brake cleaner

On 1/4/2020 at 8:30 AM, tetert1 said:

One odd thing I notice in this picture is it appears that the end of the return line is enlarged for maybe 1/2 inch or so. Is there a possibility that there's a one way valve in there so the fuel can only exit? I haven't seen a 73 this close for almost 30 years so I'm just guessing. I don't recall my series 1 car having that enlarged end when I had the line off it a couple of years ago.

I believe they all have that. A remnant of the swaging process

I was going to tag Jim but I don't know how to do it from my phone

I'll second the above. All of them I've messed with look like that and there's no check valve. Just an orifice.

I suspect your orifice is plugged with crap.*

 

*Don't you just hate that?