Im trying to figure this out without taking it to the expensive shops. I have massive engine vibration around 1500-2500 rpms. It seems to be getting worse as time passes. I have ruled out motor and tranny mounts as they are recently changed and checked again. The motor is a 5.7 and carbed. tranny is a 5 speed not sure what out of. I had bought this car about 4 months ago been driving great until recently I have been getting some vibration. Started out slow and not so forceful but then it started getting worse. recent changes are mechanical fuel pump instead of electric. I have had firestone look at it, they say mounts great but don't know about the vibration. said possibly engine needs balanced. Any suggestions that may help me out and ease my mind. Oh and when you rev the motor from engine compartment I cant hear any misfire, vibration; noise and feeling. This happens when I drive, or neutral it doesn't matter, when it does it consistently. Any help is appreciated.

sounds lke something with the clutch-perhaps bad
pressure plate or missing or wrong pilot bushing.
Clutch work good,not chattering or grabbing?

Just to be clear that the vibration comes in when the car is not moving?

Yes happends even when car is not moving. and to also be clear when i push the clutch down most gears work great sometimes mostly going into reverse it grinds bad. like its not engaging. Could that be the vibration, im actually really lost here. makes sense considering I have noticed some clutch issues around same time vibration started. And both getting worse at same time.

That's the first place I'd look. And I'd do it sooner than later. A clutch letting go can be a messy, even dangerous, event. It's the reason they make scattershields. Too many racers back in the day got their feet amputated by exploding clutches and flywheels. Of course, they were turning much higher RPMs that you are driving on the street but there's still a LOT of inertia in a spinning flywheel and clutch assy.

Internal engine vibrations don't just "happen" all of a sudden.

You can also check the front accessories as the cause of the vibration by temporarily removing the belt(s) and see if there's any difference. But I doubt you'lll find that to be the case.

I have been reading about when the clutch is starting to go out and people talk about slipping and or losing power. I have had neither happen, once engaged its great and no loss of power except that i know i need to time my car again. but no loss of power when im on it or slipping of gears. but ima check it out anyways

SLippage comes from a worn out clutch disc. All the material wears off and it doesn't want to grab any more. A broken clutch is something different entirely.

Im going to look into this broken clutch and see where it leads. I would imagine that if it were broken it wouldnt work at all...meh im still lost on this so ill try anything anyone says to see where it gets me. Ill let you know

Could this be a harmonic balance flying south?

noticed your speclist shows 350 installed-possibly when
that engine was swapped in,no pilot bushing was
installed in the crankshaft-that will allow the clutch
disc and tranny input shaft to run off-center a little
and cause major vibration and eventual major tranny
damage.Missing pilot bushing will not cause vibration
if engine revved with tranny in gear,clutch in,car
stopped because the disc will not be rotating.
A missing or badly worn pilot bushing usually also
causes clutch chatter,rough engagement,and other
clutch problems besides vibration.
could look at the harmonic balancer too(behind crank
pulley)to make sure the outer ring has not come
loose off the rubber and wearing against the timing
cover.

Awesome ideas and im going to look into them to see what i can find out. I dont know if anything was forgotten off the motor it is how i bought it. This guy was kinda off anyways I had to re-wire the alternator, install clutch fan re-run gas lines and what not. Its been fun and my wife is starting to get irritated lol

Ok quick update. I don't know how much space between bell housing and oil pan. But I have a decent gap there and oil leak from there also. Will check more on wed.