I had a very nasty tramping situation in my datsun 1000 after I swapped my drag motor in.

I swapped out the standard springs with the modified leaf (re-set) springs from the drag car in to the old fella along with all new urethane bushes, it still trapped like (some tramping thing).

I had all but given up, and changed my driving style to suit. I thought that the pinion angle may be the culprit, so I swapped the drag cars diff (re set 15 or so degrees up) but it was still tramping like a tramping thing.

Turns out (no word of a lie) I had a dream, that the standard engine mounts ( original 1967 items) were to blame.
I got the trusty mig out and whipped up a new solid passenger side mount and trans mount, And shiver me timbers.
It seems so obvious now but hey.
It doesn't take long, or much effort to solid mount your motor (It does vibrate quite a bit at certain revs).
It cured the tramping issue in my car. Maybe you need to swap out your engine mounts out for some stiffer ( urethane or solid items).
Hope it helps.

G