ive done the conversion to my 1200, its pretty simple, there are two tricks

1. when you take the auto off, then the torque converter (thing on flywheel that autos have) you need to get a spigot bush to put into the flywheel, this is where the shaft from the manual box slides into as a guide/balancer

2. the 2 boxes mount difrently at the back so you need to make up a new gearbox crossmember

if youd like me to go through and explain the entire procedure let me know, its just these are the two tricky bits

oh, the tailshaft is the same for the two gearboxes in a 1200 anyway