shaking all over the place?

[[JP]]

So.. have had my 65 C10 since Christmas and havent managed to have a proper drive yet!
mine has a 69 350 Buick engine in it, and I've been having running problems with the timing not staying steady on idle, just moves above from 4deg to 0, fluctuates now and again..
and when driving, if you are steady with it its fine.... then you give it some flat pedal accelaration, the truck flies with loads of power and then starts to cough up....
I have to ease off the power and then slowly accelarate, almost waiting for it to 'catch up'

I have one of those micro 12S fuel pumps, dont know how noise those things are but mine I can hear it in the cab! are they supposed to be that noisy? what about fuel delivery? does this look right? because from what I've described above it almost feels like fuel starvation and the pump seems to just dribble?

Fuel flow... - YouTube

anyway, that is kind of being sorted, but today on the last test drive, it all went wrong.
suddenly there was this shaking, almost like when you have a flat tyre, flump, flump, flump....
didnt shake me inside it or felt it on the steering wheel, my friend who was with me said it felt like something at the back, so we got home and put the axle stands on and found there's no play on the passender side, but the driver side I have this much play?

is this bad? could have this been the cause? how do I go about fixing it...?

C10 axle play - YouTube

thanks!
JP