Karl,
Don't be put off so easy!
sorting out gear selection will be far more challenging...
I cannot recommend anyone to modify your VW.
I'm almost sure late P901 CV's will foul the top of late swing-axle T1 frameforks, if stock engine position is retained. Clearancing may comprimise the structure somewhat. Never forget your VW is old.
A BJ framehead on a duty-free '02 'pan, or better still a stickshift with dead box, go for it. Pay no more than £300, with/without bodyshell
You will have read that this swap is a body-off operation and the cost of that can all too often hit ~£4000 just to get it to bolt back up if less than A2 condition, sadly. Consider the health of your heater channels before 5gears. If you tackle it yourself, you still have to pay through the nose for that modern car, I tell myself
Matt