You can swap the 1L box for a 1.3GS box, the final drive ratio will be much better for your usage - if you stick with the 1L three pot box 1st gear wont be that much use, so it's more like having a four speed box. And yes, it's a straight swap, no mods involved at all.
Swift 1.3GS boxes come up on ebay ....you are looking at about £100, less if you can source it privately.
The subframe mods are very similar to what you need to fit a 16V GTI lump, so as Minuki says take a look on the 16V forum and you will see what you need to do.
You can source a complete 1L swift for well under £300 as a runner, so that gives you everything you need ...may advice is to use the compete Suzuki loom and just attach the mini end bits (lights and indicators) ...keeps it really simple.
I'd stick the alternator under the wing ...it works 100% and it's tried and tested,
Edited by DomCr250, 21 January 2014 - 05:48 PM.