You can get manifolds that rise a bti don't flow as well though...
I don't think the GT head makes a diff.. all the mk2 heads are the same with big valves... i think? its the older non 711M engines that have small valves...
To be honest i like the 1600 better.. way lighter just better to drive... and you don't aev to muck around putting the 2L in... no cert needed either.
i would go for the big 1300 pistons if you ccan afford it woudl go fucking hard i should have done it but couldn't afford cos you need all new bearings and bolts etc.... and my bottom end was in good cond..
Big carbs a nice idea.. sideys won't use that much more if they are tuned right... and apparently when you are running a lumpy cam it will idle way better with sideys.