That right angle bend near the bottom is going to be a btich to get the wire through.

The issue is that there are no open slots in the top of the box. The one I will free up (orange cable coming out the top) is directly below the transformer in the junction box.

I already have a conduit bender.

Oh, I see your new conduit on the rafter. Go through the empty stud bay, drill through, come up through the bottom.

You can run your romex through the same opening as an existing run. Isn't there at least one opening with spare room?

Looks like it's a pulling EL.

Move some romex. Big cables get priority...... ;)

I put pulling elbows at both ends of the 20' straight run. I figured it would be a huge pain with thick wire otherwise.

Would flexible conduit be okay for that final run to the main panel?

My plan is to purchase the 6 gauge wiring and 50 amp breaker next Friday.

Where is the main panel located? Basement?
If the walls are not structural in any way, remove a stud on one side and move it over.
Typically plenty of knockouts on the sides of those residential panels. Pull the front cover of the panel and check this before making any changes and check your local code.
If you are using hard conduit all the way to the panel, I would suggest a pull box instead of the pull LB that you have on the end. Easier to pull you wire (Rawknees should be commenting shortly) through the box and you can leave a bit extra looped in the box in case of any changes down the road. YMMV.

edit;
Empty flex is fine here for that last run into the panel.
The two hole straps you are using for the emt would not pass inspection here unless both sides were fastened to a 2x4 or some backer.

The panel is in the walkout basement. Those studs are holding up the house.

Yes, I realize that I need to put a 2x4 between the floor joists to support the second hole on the strap. That's on my to-do list for today.

When wiring the box (and the 50-amp breaker), does it matter which is red and which is black?

No. They can both be black (or red) also.

Think I've got the conduit squared away:

http://forums.pelicanparts.com/uploa...1587335805.jpg

What a mess! I opened up the main panel. A previous owner sprayed foam in the panel. Not sure this is a good idea. Also it appears that ground and neutral are the same. Is that common?

http://forums.pelicanparts.com/uploa...1588032053.jpg

http://forums.pelicanparts.com/uploa...1588032154.jpg

http://forums.pelicanparts.com/uploa...1588032249.jpg

http://forums.pelicanparts.com/uploa...1588032361.jpg

^That looks seriously dangerous.

There should be a main shutoff of the panel to the street, I hope.
Take it slow and safe.

AFAIK, Common returns to the source.
Ground is to a copper ground rod stuck in soil. Literally. A last resort safety measure.

I once read about a SF BART electric train station messing up an entire surrounding neighborhood because of a common vs ground problem.
(there is a lot of juice flowing those electric trains)

That is NOT OK.

The grounds and the neutrals should be on different bars. Eventually, the neutral IS grounded, usually in one spot. But mixing the grounds an neutral on the same bars is not done.

Here is an example.

https://diy.stackexchange.com/questions/1706/is-it-ok-to-have-mixed-grounds-and-neutrals-on-bars-in-a-breaker-box

I am not sure about the specific spray foam insulation, but that does not look like fireproof. If arcing occurs on a loose wire, it could ignite the insulation.

I think you need to get a professional in there to look at this.

Not only not fireproof but poisonous gassing in a fire: Common Polystyrene spray can foam insulation.

One point. The WHOLE REASON for having the electrical connections in a metal junction box is for safety. Adding in flammable insulation negates this.

Chris, you may end up having to replace your main panel.

Also with a small amount of moisture in the foam, it can become very much a conductor.
Someone ****ed that up big time.

It might be easier to get a loaded (with breakers) panel from the Home Despot (as Sammy calls it) and rewire that mess.

That is nasty.

Funny, I had the house inspected by an electrician before purchase and there was no mention of the foam or the confusing neutral/ground.

I strongly suspect the foam is fireproof. It's available at Menard's and looks the same as the polystyrene foam. The previous owners were obsessive about energy conservation.

Oh me gawd. I have never seen that done before (the foam, not ground. That's not good neither). Yep, like many said above, its time to install a new panel. I am almost temped to ask you to loosen up the wires and use a plastic scraper, try and scrap out some of the foam to save yourself some money. Sometimes, they are a btich to get out. Take the feed wires off the lugs, wire nut them, tape and scrap away. It may not be worth the saving for you due to the danger. Plus, you look like siht with curly hair.