OK, didn't build this thing, 65 Dart GT, 79 360, trunion 4 speed, 7 1/4, has the hump, vin says /6. I haven't dealt with SB's except Poly's, how do Ya think they put this together?
79 360, ~240hp with a 4bbl
69 318, ~230hp with a 2bbl
65 273, ~235hp with a 4bbl-Commando
Like said;7.25 will be first to go; BUT
if you put a SureGrip into it so it cannot peg-leg, and do not do neutral drops, and install fresh Extreme-Pressure gearoil, plus the SG additive; then the spiders can last a reasonably long time.
All Mopars have a spider to sidegear ratio of 2:1, so anytime that ONE tire is spinning, it will be doing so at TWICE the Speedometer indicated speed. So if the speed-O needle is on 40mph, the wheel is at 80mph, and the one side-gear is stationary, while the other is madly whirring around, and casting it's oil off as fast as it can, and soon yur cooking the oil, which begins at about 250*F on uncontaminated fresh EP gearoil, while those spiders are heating up the crosspin, which can easily begin to seize.
Over-heated oil is full of hard carbon particles and is not a very good lubricant, nor a coolant..
The point is, Peg-Legging is bad.