360 engine vibration

Thanks guys, great feedback,

I will recheck the converter , but im sure it's fine and that is just as shadow in the photo.

It vibrates in neutral, park and in drive (I had a sneaky drive down the road) it feels like it not running on all cylinders but ive checked the plugs and leads and checked all firing. I'm going towards a balance issue, as I think I see external balance on the front and non on the rear. The engine I think is's a late 80's 360, I have a photo of the engine number somewhere I'll post up a photo of it. Only other thing to thorw in the discuss is at present its running open headers as i need to make up the exhaust, but i can see this causing the issue??

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