mk4 or corrado dash??????

HI everyone, i've had a mk1 golf gti for nine years now, and have been modifing it for the past three.
As standard i've converted a 20v turbo lump under my bonnet along with all the drivetrain  , now comes the tricky part,  
I can't decide whether to install a mk4 dask with all the instrumentation and complete mk4 wiring loom 8)    
or
Custom engine management with corrado dash and modified mk1 wiring loom to suit. :twisted:    
If i go for the corrado dash, is the speedo a digital signal because i've already installed the mk4 gearbox which has a digital output?