1976 Dart Overheating and other issues

Yes, this is my first vintage car so I am I new to it. I’ve been reading a lot on the forum for how to get things done.
The advice to relay on the shop manual and Chrysler's Tech Bulletins is a sound one.
A lot of keyboard mechanics on the internet. Starting with a good foundation will go a long way in seperating the chaff from the wheat.

I found a shop local that specializes in radiators. I’ll make an appointment.
That sounds bad.
A radiator shop doesn't specialize in radiators.
Shops that say they specialize in radiators are usually general repair shops.
Call the shop and ask if they rod and clean radiators. Ask if they solder. If the answers are yes, then bring them the radiator. Some will let you bring the car and do the removal and install. if they answer yes to the first two, you could ask them about that if you really want.

To the poster who mentioned to check the timing, My sticker on the fender says timing is to be at 2 degrees BTC.

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if you turn the photo horizontal before posting it will appear larger in the post.
The forum software resizing feature seems to allow about 800 pixels horiz but maybe less vertical.

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Note the other information with respect to timing. In particular, 2*BTC plus minus? 2* at 750 RPM plus or minus 100 rpm.
Also further down, to disconnect the vacuum advance canister. On the slant six, its often easier disconnecting the hose on the other end and capping the manifold source. Reconnect after setting the timing.

However since you've found a leak, and the system wasn't even hot yet, its pretty clear this is the first thing to address.
Any leak means the system can't hold pressure. Fix that.
The engine bay looks clean and that may be the only big issue.
Since the car has A/C, there will be a condenser in front of the radiator.
If you remove the radiator yourself, just take your time and keep track of all the parts. Its not hard. Be prepared for ATF to drain out when removing the transmission lines. Use a pair of 'line wrenches' when breaking the nuts free.

www.Mymopar.com has many of the Chrysler Tech bulletins and films, along with scans of some factory shop manuals.
www.imperialclub.com also has many Chrysler tech bulletins and films, but less so for mid and late 70s.

Hopefully you have the owners manual. Not many, if any, are available digitized. For paper copies of manuals, originals and reproductions are available from various sources. Bishko is a big vender with good rep.