http://www.theminiforum.co.uk/forums/topic/8689-internal-shifter/page__p__92394__hl__gear#entry92394
I bought 2 1/2" drive socket set UJ's and used the female halves to make one joint, cut the selector rod about 3" fromt he gearbox end and weld the ends into the UJ making sure you keep the role pin holes in the same alignment they were in originaly (I made a jig out of a peice of wood and 2 nails). If you don't get them lined up to how they used to be, then the gearstick housing won't sit straight and you'll loose gears.
I cut the rod down a bit to keep the over all size the same once welded up as when it was original. Cut a hole just above the tunel were it joints the bulkhead and conect the UJ end of the shaft to the 'box and the other end back into the gear stick housing. Because the housing has been liften heigher than its normal place, I needed to cut about 5mm off the housing were the steady rod bolts in to compensate for the fact its a fraction closer.
I used the original housing hanger bracket and turned it upside down and bolted it all back inside the car.
I tried another version of it with 2 UJ's, but it didn't work so ignor the UJ nearest the gearstick housing in the pics.