Are you able to take photos of the fender tags at a slightly different angle? Sometimes lighting and angles of photos hide certain things on fender tags. I don't want to give away too much because there are a lot of unscrupulousness people out there that try and fake stuff! And a 340 WSS is...
Your camshaft is actually pretty big compared to a stock camshaft. One trick to get better idle at lower rpms is to drill a small hole in each primary throttle blade. This will let in a little more air at idle. If you don't have a set, get some numbered drill bits and start with a #45 and see if...
I run 195° thermostats in every car I own. If I remember correctly, when we had the 70 Challenger roundy round race car, we used a 180°, but it never ran more than 100 miles between races!
The ground strap going to the engine block to the bolt holding the voltage regulator and ECU bracket that @Challenger RTA posted above is a must for all our old Mopars!
Anyone looking at this post and doesn't have a similar ground to the engine and ECU, go but one and install it! Even if you...
My 70 Challenger "Kitten" is a Western Sport Special (one of the 381 with a 383). The 340 WSS are the rarest. Most WSS were built in the Los Angeles plant, but it closed in mid-1970 and all 70 E-Bodies were built at Hamtramck plant after that. And Hamtramck is notorious for doing things a little...
The lenses are melted in place from the factory. So when you remove the old worn out ones, you'll take some of the plastic with them. So, yes, you're going to need to solder a couple of small dabs of plastic to secure the new lenses.
Since I have both, and it sounds like you have access to both, I'd go with the soda blaster first. The soda blaster will gently remove the black paint. Then clean everything up with the pressure washer.