Cheers Tom! Learn something new everyday!
Tom, with forced induction the bike carbs are waste of effort, the extra air the carbs will flow on a N/A engine will be irelivent on a "low cost" supercharged setup, it will just make it very complicated and tuning/timing will be a major ball ache
If you have the carbs and are determined to use them, then junk the low compression engine you have for a multi-valve HC engine. A 9a or 6a 2.0 16v with a 1.8 kr inlet cam will see you in the 160-170bhp region and would be mighty screamer in the MK1. Yes there are better engines out there, but with a VW unit there will be no fabrication involved as this will go in on your original mounts and bolt up to your 020 4E box
As for your 1.5, you would be suprised how little it would cost to turbo it using mainly used parts, and megasquirt is sooo cheap for what it does, this also gives you the option to use a supercharger with the ability to get the fueling & timing spot on