th350 transmission please help

[85WorkTruckDeluxe]

hello my buddy has a 76 scottsdale LWB 350 th350 combo the transmission shakes the whole truck in park, neutral, drive and reverse it also shifts late and hard and refuses to let the truck go faster than 55mph above 55 you can step on the gas as much as you want but the engine will just free spin, the shakeing smooths out a little around 1500-2000 rpm but dosen't completly go away. the torque converter bolts are not missing or broken we changed the fluid and filter and there were no metal shaveings in the bottom of the pan. its got me stumped any help will be greatly appreciated