You need 2 plug GTI clocks, IIRC the 1.3 will have a 120mph speedo which means a set of 120mph MFA clocks should work perfectly fine as far as avg. speed/distance/time etc go. To get the MPG working you just need to find a carby in your scrappy and pinch one of the many 'Y' splitters they have on em, and split off a line to the clocks from one of the feeds to the chunky brake servo pipe.
I found the mpg display to function very well and give me good accurate values on my 1.6 Driver
You'll also need an oil temp feed as well as an outside air feed, the outside air sensor can be found clipped to the inside of the passenger wing, just behind the bumper. As for oil temp, this may be tricky on a 1.3 but you can get oil 't' pieces, deamon tweeks sell them, you need a M10x1 threaded one
Now the wiring on an earlier MK2 is a little tricky, but easily doable. You need to gram the MFA stalk, then follow the wiring plug as far as you can. If you're patient you should be able to follow 3 of the wires all the way to the dash plug, and the earth back to the earth 'claw' near the fusebox. To make the outside & oil temps, cut the plug off a pre 90 GTI (so you can use the ends and splice them into your dash plugs) and run wires to the sensors.
Check out this handy-dandy guide for more detail, and the locations of all the pins:
http://forums.vwvortex.com/zerothread?id=295039
