It's all 'OUT THERE' cause we can't see and feel it....One guys 'tick' is another guys 'rod knock'
I kindda chose the clutch and trans cause he says the motor runs fine and the clutch ped in my 39 make a 'Hell Racket!!'
What happens is the clutch and trans are turning all the time the motor's running If the clutch
isn't centered you get a shake....it will vary a bunch if you leave out the pilot bush. Sometimes at speed it will center sometimes not.
I mentioned the bolts cause it's a easier to see if that's the problem.AND it will do just these things also.
Tab...If it all looks good ...get under back off the pressure plate bolts and try deflecting the input shaft....if it moves that's it! and look at the flywheel.If there is runout also it!