I have been having the same problems with the same truck. The slow speed singing went away when I changed the pads (only part used) from a store brand to Raysbestos. I still have the slight pull and the intermittent brake light. If you try the hoses will you please post your results...
I am preparing to pull the slant 6 from my 72 scamp (putting in a 440) and I don't have space for another engine. It has 83k on the odometer and it ran when parked in a garage 15 years ago. It turns over and ran by pouring gas in the carb. I am asking $250 for engine, trans and 7.25 rear, or...