This is a query to list experts- my trusty 78 Westy (no problems except
usual pushrod seals and heater box replacement) started a "rattle" at
deaccelation about 15,000 mi ago, and I think it's worse now- not
transmission, since you can do it when parked and revving up engine with
clutch in.  Not throw out bearing, since it sounds "too deep" and can be
done when car is in neutral. When you push the clutch in to shift you hear
it until shift is completed and put it under load (give it gas); also while
deaccelerating on open road you hear it until a certain lower rpm is
reached, or if you step on gas again.  I've had rod knock in a bug, but
that was more of an isolated "clatter" as the one rod swung around; this is
an overall rattle, like maybe main end bearings, camshaft bearing?  What's
odd is that you don't hear it so much when standing back by engine, but
"feel" it through the floor and especially when holding onto shift lever-
in fact when I first had it I thought it weas trans related since you could
lesson vibrtations somewhat by holding the lever tight- but isn't trans not
involved when clutch is in and you rev it?  Any one ever experience this?
The oil pressure is OK, compression still around 120.  MB in NJ