It's really rather charming (except the dildo-for-a-gearshift) and takes me back to my childhood. My dad ran a blue GXL for a couple of years before trading up to a Maxi
I'd be tempted to stick a Rover V8 in it, maybe even an LS, but keep it looking stock
I feel old now, but I had one as my first car, ermine white with a black vinyl roof. K reg too. It was 3yrs old when I got it and it was pretty knackered even then - rust coming through the top of the wings etc.