Are you sure its a 2.8 and not a essex 3.0 if its carb'ed, here's my dads mk2 with a 3.1 essex.

Tuning wise not that easy to do tripple webbers cost a small fortune or a 4 barrel holly is a cheaper option both of wich you will have to cut a hole in the bonnet to fit.

A 38 carb, cam, lightened flywheel and headers are the most realistic mods.