E body drum brakes....still not right

Thanks for your help on this post in the past. 70 Challenger, master cylinder was empty after 6 months storage, no sign of leaks, manual factory drums.could not get all wheels to bleed so I replaced m/c, bench bled. Replaced rubber hoses, replaced wheel cylinders. Tried bleeding with a vacume pump but the pump would not draw fluid from all the wheels. Tried gravity bleed didnt work. Tried the good old fashioned pump the pedal. Seemed like they bled. Test drive, exactly the same as when I bled the original system. Firm pedal, step on the brakes and the steering wheel jerks from side to side and one front tire begins to skid. Car stops fine however you practically loose controll. The brakes worked fine for years when I parked the car. Bled it in the past with no problems. Dont know what yo do at this point. Ive tried everything I know.....any help woild be greatly appreciated.

Seems it's only the front wheels that are bothersome.

?fluid soaked linings? Front (shorter)
lining) shoe and rear shoe swapped??

sounds like the lines are blocked. at this point i would go to a brake shop and have the system bleed out on a power bleeder to flush out all the old fluid and hopefully any build up inside the lines.

If it's pulling to the pass side then the DR side ain't doing it's job for whatever reason (& vice versa). Could be the linings ain't spooned up far enough on the offending side but you did mention blockage issues. I'd undo the particular lines & blow em out if I was sure there was inadequate psi at the bad corner

Rust on the drums can make them grab. Not sure its your problem but it may be. Some careful stops from speed on a lonely highway will clean them up.