[urq] subframe perhaps?

[SpotatAshleys]

Lately I seem to be fighting fires instead of enjoying my quattro. Starting, clutch, alram and on and on etc.
Anyway the latest problem to blight my free time is a clunk in the front end somewhere.
It is noticable at all speeds, is intermittent, doesn't seem to correlate specifically to acceleration, deceleration,braking or change in direction, it just happens. It is sufficient to "feel" through the floor and pedals. There is a slight tendancy to wander with the camber of the road but it is very slight. I put this down to the 8in rims. The car has had new shocks (bilstein), top mounts, control arm bushes, steering arms, anti-roll bar bushes, wheel bearings, ball joints show no play and everything is tight and tightend to factory settings. It has got worse since changing the clutch a few weeks ago when the subframe was lowered to allow access to bellhousing bolts etc. The subframe mounts are in line for replacement. 
The question is: what else could it be? I'd like to cover all bases when I do the subframe mount job and fix this clunk once and for all.
At the moment I feel a bit like a test pilot, wondering if the thing will hold together.

Also I believe the front subframes of the coupe quattro and the urq are identical. Can anyone confirm this?
I have a cq subframe that I intend using and simply do a subframe swap (new bushes of course) and don't want to find it is no good when I'm half way through the job.
As usual, any help gratefully received.

Cheers

Keith

'87 urq