Most of the usual suppliers, VW Heritage, Machine 7 etc. do 1641 kits with new cylinder heads, gaskets etc. To make the best of this you could really do with upgrading to twin carbs; Kadrons or Weber 34ict's to really liven the engine up, plus a 200mm flywheel and matching clutch.
As Snoopy says only do this work if you know that your bottom end is 100%, ie factory spec endfloat and good oil pressure.