I see what you're aiming for here, you need to look more 80's angular design than 2k+ designs the Mk1 is over 25 years old and some stuff just doesn't look right IMHO.
Have a look at AEK's front bumper and see what you think of that
I personally love this design as it suits the shape of the car more...I'm sure you can elaborate a little on this using some desing que's from Mustang or Aston Martin etc to keep the "look".
Don't give up, we're all climbing the slippery slope of development and we will slip a few times before we get a good grip.
Best of luck with your efforts.