Mopar virgin checking in with new 1969 Barracuda - with questions.... ;)

Greetings again, folks! Boy this place has become very active! My thread used to stay on the front page for months and months and months....now after 3 months it's dropped to page 7!!

Steadily I've been trying to fix the small problems with the car. I had an electrical problem (still do, I think!) and the engine wouldn't start. Turned out it was a burned out coil. However, after installing a new coil, it runs great. On the other hand, there's a part on the carburetor that's getting really hot so perhaps that's what burned out the coil. One of the wires from the coil was going to the carb and my father in law simply removed that wire and now it runs OK with no overheating to that part of the carb. I need to figure out what the wire is supposed to be doing....anyway, there are other problems. I decided to take her for a run while the engine was running and noticed a valve clicking or something like that. So when I returned, I decided to replace the oil in this "new" 318. Turns out that the oil was "slightly" old. Very dirty and surely not doing its job. Now why would anyone pour dirty, used oil into a new engine? ;) So I was probably ripped off by the garage owner when he said he put in a new engine (and relieved me of my old engine, which I suspect was original but don't know). So after putting new synthetic oil in the car, it now runs without any valvetrain clatter. Whew. And it's very quick. So I took it for a spin and during this test, I did a few burnouts, which seemed to be catching rubber on both rear tires. Recall that I have the Spring Special option on the car, which I was informed (here) that it included the Sure Grip option, despite nothing on the data plate to confirm the Sure Grip option. Supposedly if the Spring Special option was added to the car, the data plate wouldn't list all those options in the package separately on the data plate. So I always suspected I had a Sure Grip. However, I've known cars with open axles to spin both tires on smooth surfaces where there's not much traction. So I also took off the rear axle cover, drained the rank, smelly fluid and did some research on here as to what is inside. By all evidence, I do NOT have a Sure Grip. I can see all the spider gears inside the 7.25" axle and no evidence of any springs or cone pack or anything like that. Inside, my differential looks exactly like a non-limited-slip axle. So I am major bummed about that. It's a 2800275, 2.76:1 dated 2 11 69, which corresponds directly with the 2 22 69 build date on the data plate. Also, there is play inside so I need to be careful with the burnouts because this axle needs to be rebuilt. Otherwise it looks great. So I can assume that the Spring Special package did not necessarily include the Sure Grip axle.