Purchased 1973 duster a few weeks ago need help

Hello to everyone! I just purchased my uncles 1973 plymouth duster a few weeks ago and am i need of some ideas and help. The car has been sitting in a garage for 5 plus years. It was an original 340 car in 1973 however the 340 that is in it now in a 1970 motor. It is a factory 4 speed with a cast iron bell housing. I did get the original aluminum one with the car. The motor was built by a local machine shop in the late 80's. Not sure of any specs but it has been bored has what i would call a mild cam and an edelbrock carb and intake with the factory 1970 heads assuming they have had some tweaking done to them also. To get it running i had to install a fuel pump and filter and put all new rubber fuel lines up to the carb. Upon getting it running i attempted to back it out of the garage. That is when i notice the front wheels dragging because the pad had rusted to the rotor. Got it cleaned up enough to drive a short distance home and noticed lots of pulling towards the rusted rotor side that i cleaned up and just seemed like tons of drag on the car from the brakes. After getting it home i re did all the brakes. Calipers....pads...flex lines front and rear....shoes...wheel cylinders and all drum hardware. All wheels spun freely on jack stands and seemed to bleed out fine. I am still feeling like there is drag or something holding the car back. I have jacked it back up and everything spins freely. Could this be a carb issue from sitting? also I have notice a bad oil leak from the oil pressure sending unit at the back of the intake manifold. Is there any way this oil could be churning up into the bell housing somehow and getting on the flywheel? If the car sits for a few days and the oil dries up the clutch seems to feel much stronger and more responsive but as soon as i go do the street and back the clutch feels weak as if it is slipping. Also the 4 speeds first gear seems very rough on take off like it is lopeing or bucking real badly and smooths right out after getting up to speed? I own and work on 3 mopar 4x4 trucks so I am somewhat used to my way around mopars but this is my first a body. Any help or suggestions would be greatly appreciated!

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