How?
The na engines in the mk4 only produce 115 and 125bhp i think?
Oops, typo...meant Mk3.
The fact remains -
You just need a different FD, Quaife diff, a bottom end good for 7500-8000 RPM and considerably over 200 BHP.
More traction, lower gearing, more revs and lots more power and torque will see you under 7 seconds.
If a lardy Mk6 will do it, with 210 BHP...a low geared Mk3 with similar power but less torque, and a good 200 Kgs less mass to lug about, will do it.