Col Reb I am kinda of a Mustang fanactic. Yeah the 390 of 68 was somewhat of a dissappointment, but with today's techonology, ie: carb, intake, roller rockers, heads and headers, the 390 would have been a beast! Easily putting out 400 hp / 400 tq. I agree if the 68 Stang had a 478 Cobra Jet, no contest. But against this Charger it more than held its own.
Its fun tooling around and more importantly driving around in my 66 Mustang. It has a wide assortment of modifications/goodies, but to the naked eye it looks like it came off the showroom floor in 1966. The biggest and best mod is installing a Tremec 5 speed. Great for freeway driving. I could go on and on what I have done to her. If you want to know just ask.
Also, LSD stands for Limited Slip Differential. It provides for grip on both rearend tires, especially on acceleration and it turning. Open rear(most cars then and today) provides just one wheel, usually the right rear. Once you go LSD you will understand and feel the difference.